Biogas: exploitation of a renewable energy in Latin America

RenewableEnergyVol. 3, No. 6/7, pp. 763 779. 1993 Printedin Great Britain.

096(~1481/93 $6.00+.00 PergamonPressLtd

TECHNICAL NOTE Biogas : exploitation of a renewable energy in Latin America J . - Q . N I , * H . NAVEAU~" a n d

E . - J . NYNS~"

* Hangzhou Rural Energy Office, Qingtai Street 1', Hangzhou 310016, Zhejiang Province, China; t U n i t of Bioengineering, Catholic University of Louvain, Place Croix du Sud 2/19, 1348 Louvain-la-Neuve, Belgium

(Received 28 September 1992 ; accepted 29 October 1992) Abstract---Exploitation of biogas is scrutinized in Latin America. Among the developing countries, biogas technology has been most widely applied in this region of the world. Four sectors are successfully using biogas. In the agricultural sector, 9440 digesters have been identified. In the industrial sector, 25 types of wastes have been either investigated for biogas production or are already in full-scale application. Latin America is now the world's leading user of biogas technology in the municipal raw sewage treatment. Thirty-three R & D projects have been reported. Since 1977, five projects of biogas exploitation from sanitary landfills have been implemented. This makes Latin America the leading user of landfill gas technology in the developing countries. High-rate biogas fermentation processes are being developed and increasingly utilized. Several techniques of biogas treatment have been applied. Biogas is mainly used for cooking, lighting, as town gas or as vehicle fuel. The quantity of biogas produced in Latin America is estimated at 217 million m 3 per year. Future R & D in biogas technology requires not only technological efforts, but also incitations by national governments and non-governmental organizations (NGO) in order to promote favourable conditions for the exploitation of this renewable energy.

1. INTRODUCTION The use of biogas as a renewable energy has a history of nearly a century in the world. Because it has multiple benefits, including energy generation, pollution removal and other economic, social and ecological advantages, biogas technology has been intensively investigated and more and more widely implemented [1-5]. Biogas as renewable energy in the developing world is chiefly characterized by a large number (about 6 million) of rural family-size digesters. But its application has also started in industrial and urban sectors. The exploitation of biogas in the developing nations is a rather complicated process. The reason is that these countries are usually faced with many economic, social, technical and ecological problems. They have more or less direct or indirect impact on the implementation of this technology. However, it is because of this, that the successful development of biogas could result in multiple benefits. The actual situations of biogas in the developing nations differ fi'om one to another. In some countries, development of biogas programmes has lacked urgency because of the readily available and inexpensive conventional and/or traditional fuels [6]. In others, accelerating diffusion has been planned for the 1990s, namely in India, Nepal and Ethiopia [7 9]. In still others, shifts in sectors of application, and changes in technologies and in implementation strategies can be observed. Latin America is a representative of the latter group of countries. Like most of the developing regions, Latin America suffers an energy problem with the exception of Mexico, Trinidad and Tobago, and the Andean Group in South America (Colombia, Ecuador, Peru and Venezuela). Almost all Latin American countries are energy-deficient [10, 11]. On the 763

other hand, Latin America is faced with an increasing problem of environmental pollution, chiefly caused by industrialization and urbanization, as well as ecological degradation, of which lack of firewood is one of the major reasons, the consequence of which is deforestation [12 15]. However, as a developing region, high cost and sophisticated technology may not be appropriate to solve these problems. It is in this context that biogas technology has been selected and developed in Latin America. Although the overwhelming majority of digesters are now found in Asia, the widest application fields are realized and some remarkable technical achievements are reported in Latin America. These, together with others, contribute an important part of the world experiences of application of biogas as a kind of renewable energy.

2. A GENERAL VIEW OF BIOGAS IN LATIN AMERICA In the developing world, there are now 53 countries or regions where there are biogas R & D activities. The Asian countries started their first trials at the end of last century, while Latin America and Africa began their efforts in the 1930s. To date, Latin America is the region that has realized the widest range of applications of biogas technology and has the largest number of countries or regions that participate (Table 1). However, the number of full-scale biogas digesters installed in Latin America lags far behind that in Asia, where China and India are the two largest rural biogas users in the world. Still the figure for Latin America is nine times higher than that for Africa (Fig. 1). The present scrutiny leads to the conclusion that the devel-

764

Technical Note Table I. Comparison of full-scale applications of biogas in Latin America with that in Asia and Africa Latin America

Asia

Africa

1930s

1897*

1930s*

Yes Yes Yes Yes Yes 28

Yes Yes Yes Yes

Yes Yes

125

137

First application time Main fields of application Rural family digester Agricultural residue digester Agro-industrial waste digester Anaerobic sewage works Landfill gas exploitation Number of countries or regions participating * Ref. [6]. t Refer to Note and references cited in legend in Fig. -No data found in the literature.

opment of biogas technology in Latin America can be divided into three periods. Before 1975, the first period, a few academic institutions and private organizations carried out investigations, in as much that only a few applications were reported [37~40]. The technology remained almost unknown to the public. From 1975 to 1985, the second period, the enthusiasm for biogas was largely stimulated by the energy crisis in the 1970s and the Asian experience in biogas application. Many national governments, regional organizations and non-governmental organizations (NGOs) made efforts to promote this technology. Most of the agricultural and rural biogas digesters were installed during that period. After 1985, the third period, several slow changes have been observed. These changes include a shift of biogas implementation from the agricultural sector to industrial and urban sectors, of biogas fermentation processes from conventional ones to high-rate ones, and of changes in implementation strategies. There are presently 28 Latin American countries or regions participating in this technology. However, the Latin Amer-

ican biogas R & D activities are largely concentrated in Brazil. Table 2 points to a great importance of biogas research and application in this region. According to Caceres and Chiliquinga [41], Brazil houses 25% of the total number of research institutions working in this field. Our statistical study shows that nearly 51% of a total of 891 publications concerning biogas in Latin America issued from Brazil. The field application of biogas digesters and landfill gas projects represents even more favourable facts for the Brazilians. Besides Brazil, there are 13 countries that participate actively in biogas R & D . These are Bolivia, Colombia, Costa Rica, Cuba, the Dominican Republic, Ecuador, Guatemala, Honduras, Jamaica, Mexico, Nicaragua, Peru and Venezuela [42]. 3. BIOGAS EXPLOITATION IN DIFFERENT FIELDS According to the type of wastes, biogas applications can be classified in four fields: animal and agricultural wastes,

4 700 000

China

I

India Asia

11

1 200 000

989

9567

Latin America Africa

1060 . . . . . .

10 2

"I

10 3

. . . . . . . .

I

. . . . . . . .

10 4

I

10 5

. . . . . . . .

I

10 6

. . . . . . . .

I

10 7

. . . . . . . .

10 8

Number of digesters Fig. l. Comparison of digester numbers in the developing world. Note : "Asia" includes : Bangladesh, Bhutan, Indonesia, Nepal, Philippines, the Republic of Korea, Sri Lanka, Taiwan, Thailand and Vietnam with the exception of China and India [6, 7, 16-26]. "Africa" includes: Algeria, Burundi, Cameroon, Egypt, Ethiopia, Ivory Coast, Kenya, Mali, Rwanda, Sudan. Tanzania, Tunisia and Zimbabwe [6, 9, 27 36].

765

Technical Note Table 2. Comparison of biogas R & D in Brazil and in other Latin American countries or regions

Countries Brazil (%) Thirteen active countries (%) Other countries (%) Total per cent (%) Total number

Research institutions*+ +

Publications

Rural digesters

Wastewater digesterst

Landfill gas projects~

23/40 60/49 17/11 100/100 109/371

51 39 10 100 891

88 11 1 100 9440

88 10 2 100 127

80/80 0/20 20/0 I00/100 5,,'5

* Institutions/specialized staff. Source: ref. [41]. t Identified number, including agro-industrial wastewater and urban sewage digesters. ++Number of projects : executed/proposed or projected.

national levels and the cooperation with international organizations and foreign countries [42]. The wide range of biogas technology development and diffusion in the rural sector in Latin America started in the late 1970s (Fig. 2). Beginning in 1979, the number of digesters increased rapidly. By mid-1985, there were 8606 rural digesters in Latin America. But after 1985, the spread of digesters slowed down. Indeed, whereas the number of digesters still increased, some practical obstacles were met. According to the literature, Latin America counted about 9440 rural digesters by 1990. The number of rural digesters functioning regularly is about 60% of the total number of digesters [42]. The major part of the rural digesters are presently found in Brazil. The second and third largest users are Cuba and Guatemala. Twenty-two other countries or regions have less than 100 digesters each (Fig. 3). In Belize, St Vincent and Suriname, some biogas activities are reported [41, 51, 53] but the numbers of rural digesters are not available.

industrial wastes, urban sewage and municipal solid wastes. For these different fields of application, not only the technological aspects are diversified, but also the economic and social backgrounds differ. 3.1. Bioqas from animal and a,qricultural wastes The largest number of biogas plants in Latin America are found in the rural or agricultural sectors. These digesters use animal and agricultural wastes as fermentation substrates, sometimes mixed with human excreta, and are mostly smallscale ones with individual volumes of 7~J,0 m 3. The recent reported costs of these rural digesters range from 30 to 222 US$ per m ~ of digester in Mexico and in Bolivia [43, 44]. These costs depend upon many factors, such as digester model, size, location, construction material used and so on. Although biogas is considered as a means of rural integrated development in Latin America, for most of the farmers, the first purpose of constructing a digester is the generation of biogas as a kind of energy for cooking, lighting and other diversified uses, especially among the small farms where there is no access to the conventional electrical power grid [45]. The participation of regional organizations, such as OLADE, ICAITI, COD and CEMAT, national goverments and NGOs has contributed much to the biogas development in the rural sector. The successful experiences in rural application also include national biogas programmes, particularly the one in Brazil, Biogas Networks at the regional and

3.2. Bioyas jrom industrial wastes Industry is the field where there are more and more investigations and applications of biogas technology in Latin America. The region produces large quantities of sugar cane, fruits, coffee and other agro-industrial material [14, 54, 55]. After processing, these products leave a large quantity of concentrated residues which usually cause severe pollution problems. Biogas technology has been used to treat these residues. Besides, this technology is also chosen to treat the

12000 9440

10000

86O6

8000 6000 4000

2

Z

7

5

~

2000 0 ~ 197:

t

1980

i

I

1982

~

I

1984

i

I

1986

i

I

1988

i

1990 Year Fig. 2. Development and diffusion of rural digesters in Latin America [39, 41, 44, 46 52].

766

Technical Note Digester number 0

2000

4000

l

Brazil ~ ] Cuba

,

6000

I

I

8OOO

10000

I

18300

' 552

'

'

t

"-14

Argentina Bartmdos Bolivia Chile Colombia Costa Rica Dominica Ecuador E1 Salvador Grenada Guatemala Guyana Haiti Honduras Jamaica Mexico Nicaragua Panama Paraguay Peru Puerto Rico Uruguay Venezuela

214 I 49

214 I 50 I 65

113 I 28

"'17

""39 I 105 I 2,

""19 I 25 I 60

i32 "--"-'~

24

-"17 1,0 1 44

['~9

"'17 !

!

I

i

20

40

60

80

!

I00 120 Digester number Fig. 3. Rural digesters in Latin American countries or regions [39, 41, 44, 46, 52].

effluents other than the agro-industrial ones, such as paper industrial wastes and even petrochemical industrial residues. At least 25 kinds of industrial wastes have been investigated for biogas fermentation. Among these wastes, the investigations into stillage and coffee processing wastes are the most frequently reported. Eleven Latin American countries have been reported to take part in these R & D activities, and different types of fermentation processes have been studied (Table 3).

i ,tonnecane I

r4

v'

Pollution prevention, energy generation and the integrated use of biomass resources are the main purposes of these investigations. When the stillage produced from ethanol fermentation is treated with biogas technology, 5.9% of lhe total energy in the sugar cane can be recovered (Fig. 4). It is estimated that the stillage generated by the Mexican sugar industry has an annual biogas production potential of more than 30 000 barrels of oil equivalent [14]. To date, in full-scale application, ahnost one-third of the

1280kgbag se I --

[ 65 litres ethanol [

2.0x,0° J<53

=

,.5 x ,06 kJ (4, %)

=

0"2 x ' 0 6 kJ (6 %)

1 8 4 5 litresstillage ]

-,U2,I I0"14 m3 bi°gas I

Total energy = 3.7 x ,06 kJ (,00 %) Fig. 4. Energy balance of sugar cane (drawn according to ref. [55}).

767

Technical Note Table 3. A general view of R & D into industrial waste treatment with biogas technology in Latin America Type of waste

Research/applied country

Stillage

Argentina, Brazil, Cuba, Guatemala, Mexico Colombia, Costa Rica, El Salvador, Guatemala, Mexico, Nicaragua, Panama, Venezuela The Caribbean Guatemala Brazil, Venezuela Brazil Brazil Uruguay Brazil Brazil Mexico Guatemala Brazil Brazil, Argentina, Uruguay Colombia Mexico, Brazil Mexico Cuba Brazil Brazil Brazil Brazil Cuba Chile, Brazil Uruguay

Coffee processing

Arrowroot Banana stem juice Beer Beer/soft drink Black liquor* Casein whey Fermentation Food processing Kraft condensate Kraft paper mill Meat processing Milk processing Palm oil Paper-industry Petrochemical Protein waslewater Slaughterhouse Soybean oil refinery Starch Tannery TM Pt Vegetable/fruit processing Wine vinasse

Process used AF, packed bed, UASB, contact, hybrid, conventional AF, hybrid, UASB, batch, semicontinuous Polyurethane foam reactor UASB UASB, AF AF-UASB, EGSB UASB UASB AF, hybrid, fluidized bed Hybrid AF AF, AF UASB, EGSB Plug flow Packed bed, UASB UASB, fixed film UASB UASB UASB Contact, UASB Anaerobic pond UASB Batch, UASB AF-UASB, EGSB

* Waste from cellulose production. t Thermo mechanic pulp waste. - - N o t indicated by the quoted author. Main refs: [14], [37], [40], [47], [49], [53], [56]---[84].

biogas digesters treat brewery and soft drink wastewaters. Dairy products and slaughterhouse/meat packing wastewaters are next in the number of plants. As in the rural sector, most of the research projects and industrial-scale plants are found in Brazil. It was reported recently that there are 102 biogas plants with a total volume of 76 579 m 3 in this country [65, 68].

The installation of biogas plants for industrial waste treatment is accelerating in Latin America. An example is the number of upflow anaerobic sludge blanket (UASB) digesters for full-scale application in Brazil. From Fig. 5 it can be seen that during the 3 years from 1988 to 1991, the number of UASB installed in Brazil is about 3.4 times as many as that constructed from 1985 to 1988.

100 82

< '~

60 40

20 Z 0 1984

1 9 8 5 1 9 8 6 1 9 8 7 1 9 8 8 1 9 8 9 1 9 9 0 1991 Year

Fig. 5. Accelerating implementation of UASB digesters for full-scale industrial waste treatment in Brazil (drawn according to refs [651 and [68]).

768

Technical Note Methane 31 M 3

Influent/~ ~

(

rAnae~bieN)~

co; \ \

//

~

Energy for aeration 100 kWh

ent

cop

COD 10 kg Excess sludge

Excess sludge

ANAEROBIC PROCESS

AEROBIC PROCESS

t

Fig. 6. Energy comparison and COD balance of anaerobic and aerobic sewage systems (adopted and revised from ref. [86]).

3.3. Biogasjrom municipal sen'age Anaerobic treatment of municipal sewage has two distinct advantages over aerobic treatment [85]. Firstly, it produces methane gas, a useful source of energy. When an influent with 100 kg of COD is treated by an anaerobic process, 31 m 3 of methane are generated. Aerobic processes, on the other hand, have significant energy requirements for aeration. Onehundred kWh of energy is needed for 100 kg of COD (Fig. 6). Secondly, the fraction of wastewater organic matter that is converted into bacterial cells is quite small (about 10%) when compared with aerobic treatment (about 50%). Thus, costs, energy consumption and difficulties associated with disposal of waste biological sludges that result from biological treatment of wastewater are greatly reduced. For these reasons, such a process has been sought for over a century. This technology was widely used in the world, except for the fermentation of municipal sewage, mainly because of its relatively low efficiency in BOD elimination, especially when the temperature of fermentation is lower than 20~C. However, biogas fermentation of municipal sewage has received a remarkable achievement in Latin America. Thirtythree projects in this region have been reported, nearly half of them are full-scale applications with capacities from 200 to 6600 m 3 each (Table 4). Latin America is now the leading user of biogas technology for raw sewage treatment in the world, in spite of the fact that much research has been conducted in North America and in Europe [87]. The anaerobic sewage treatment research began in 1975 in Latin America. All reported investigations and applications were in Brazil, Colombia, Cuba, Argentina, Puerto Rico and Venezuela [ [ 3, 9 l, 92, 94 97, 99 138]. The Brazilian efforts are mostly localized in the state of Silo Paulo, the state of Parana, in Rio de Janeiro and in Brasilia. A total of 23 projects have been reported. In Colombia, R & D was made chiefly with the cooperation of the Netherlands. Beginning from 1983, two pilot UASB plants were investigated. Three full-scale systems were recently completed [98, 99, 122, 139 143]. In Cuba, laboratory-scale UASB research was reported recently [101]. In Argentina, the laboratory-scale investigation into anaerobic filter (AF) and UASB started in

CTUA/INCyTH [103]. In Puerto Rico, an AF was studied in Recinto Universitario de Mayagrez for the production of methane [96]. In Venezuela, Miragaya [49] reported two large anaerobic digesters with a total volume of 100000 m ~. But detailed information has not yet become available. Anaerobic sewage treatment is entering its stage of maturity in this region. The sign for this is the start-up of the full-scale sewage works with two 3300 m 3 UASB digesters in Bucaramanga, Colombia, in September 1990 [98]. 3.4. Biogas /kom municipal solid wastes Biogas can be exploited from municipal solid wastes using sanitary landfill technology which has the distinguished advantages of low cost and energy generation. It is estimated that in practice 100 200 m 3 of biogas can be extracted from 1 tonne of garbage with a duration of l0 20 years. Nowadays, a total of 481 landfill gas exploitation projects have been identified in the world, most of them in the United States and in Europe [144]. In Asia, Africa and Latin

Table 4. Reported projects of R & D of biogas from municipal sewage in Latin America

Country

Number of projects

Brazil

23

Colombia Argentina Cuba Venezuela Puerto Rico Total

5 2 I 1 1 33

Process used UASB, RALF, AF, lmhoff, hybrid UASB, composite UASB, AF UASB -AF

- - N o t indicated by the quoted author. Refs: [131, [49], [881 [103].

769

Technical Note Table 5. On-going landfill gas projects in Latin America

Landfill name and location

La Feria, Santiago, Chile

Fill time since Gas exploited since Surface (ha) Av. depth (m) Refuse (tonne) Gas produced

1977 1977 -20 2000/d 9000 m 3/h

Reference

[150, 176]

-

CEMIG, Belo Horizonte, Brazil

Caj u, Rio de Janeiro, Brazil

Rapozo Tavares, S~o Paulo, Brazil

--

1935 1977 100"

1974 1978 50 >20 > 1.5 x 10 ~' 9000 m 3/day

-> 8000 m ~ CH 4/day [89]

> 30 x 106 20 x 106 m 3/10 years [153, 174, 177]

[93, 157, 178]

Natal, Natal, Brazil 1986 500/day

[153]

* Gas collection system covers 25 ha. No data provided by the quoted author. -

America, there has also been an interest in this technology since the 1970s [145--158]. Latin America is a leading user of landfill gas technology in the developing world. In some of the Latin American countries, the sanitary landfill knowledge has been widely spread through courses and seminars. The landfill management technology has well been adopted in some landfill sites and developed there [112, 114, 115, 154-157, 159-175], Today, five landfill gas exploitation schemes have been reported in Chile and Brazil (Table 5). Another five projects are being planned. Among them, one is in Colombia; the other four are all in Brazil. The region has a landfill gas exploitation history almost as long as that of North America and Europe. The first sanitary landfill sites equipped with leachate t~eatment facilities were built as early as 1974 in Brazil [174]. In 1977, the city of Santiago, the capital of Chile, started a project to collect and use biogas from the La Feria landfill. In Brazil, attempts have been made by the federal or state owned energy companies, to utilize the landfill gas as a viable energy [89, 169-171]. In 1977, the Comlurb-Cia. Municipal de Limpeza Urbana (Municipal Public Cleansing Company) in Rio de Janeiro implemented the biogas collection project in the Caju landfill [153]. In 1978, the State of Silo Paulo also began the collection and utilization of landfill gas from the Rapozo Tavares landfill. In Belo Horizonte city, and in Natal, the capital of the State of Rio Grande do Norte, efforts to extract and use landfill gas have also been made. In Latin America, the exploitation of biogas from landfills is considered of significant importance. Several main benefits have been summarized: firstly, the lowering of the running cost of the landfill; secondly, the reduction of imported oil derived fuels ; thirdly, the improvement of air pollution conditions in the central area of the city when qualified methane is utilized as fuel in vehicles; and fourthly, the provision of lower price fuel to residents when it is used as town gas [89, 150]. 4. T E C H N O L O G I C A L ASPECT OF BIOGAS IN LATIN AMERICA Biogas technology has found more and more applications in Latin America, especially since 1975. Many factors have contributed to this. They include the situation of the global

energy production and consumption, the awareness of the environmental problems, the worldwide biogas research and development, and the favourable climate and ambient temperature conditions for many of the Latin American countries. Besides, the locally developed biogas technologies also have a great impact on the exploitation and utilization of this renewable energy. Most of the research projects into biogas in Latin America have been developed with emphasis on technology [[79]. Therefore, the major research achievements of biogas technology in Latin America are related to the successful adaptation and improvement of existing technologies. In Latin America, the technical applications have more significance than the fundamental research, because the multiple benefits of biogas can be achieved more directly when limited funds and manpower are available for the final goal or application.

4.1. Biogas fermentation processes Various types of biogas fermentation processes have been experimented and some are in full-scale application in Latin America. These processes can be divided into two classes: the conventional processes and the high rate processes. The conventional processes are those which were first studied in Latin America especially during the period from 1975 to 1985 and extensively adapted for the agricultural sector. This has resulted in the development of 12 different models [42]. Latin America is considered by some as "a real laboratory" where tests with and researches on all types of models have been carried out, mainly by international agencies [45]. Some of the models have been introduced from Asia and Europe, others have originally been developed in Latin America, still others are the modification or combination of the imported and local models. In the early stage, these processes were also employed for agro-industrial and municipal wastes treatment, like coffee pulp, stillage, municipal solid wastes and sewage sludge. Most of the conventional processes in rural practical use are semi-continuous and batch ones. The diversified models have not only been a unique technological characteristic in Latin America, but are also the basis of application success. In the rural sector, there exist large differences in local conditions, like types of adopters, anaerobic fermentation substrates and local construction materials. The large number of rural digester models make

770

Technical Note Table 6. Biogas generation efficiencies or rates in Latin America Substrate

Process

Temperature ('C)

HRT*

Human and animal waste

Plug flow

--

Human and animal waste

BORDA

Ambient with solar heating Ambient

Stillage of juice

UASB

28 33

2.4 days

Coffee pulp juice

UASB

35

Raw sewage Pre-settled sewage

UASB UASB

19 28 35

4h 4h

Municipal solid waste

Landfill

Ambient

-

--

2 days

Scale 8-30 m 3

Generation rate

0.17-0.28 mS/m 3 dig" day 1(L45 m ~ 0.17 0.4 m3/m 3 dig- day Pilot 11.6 mS/m 3 stillage Lab. 4.58 m3/m 3 dig" day Lab. 80 1 gas/kg COD Lab. 119 1 gas/kg COD Full 9000 m3/h

Reference [44] [44] [185] [186] [97] [93] [176]

* Mean hydraulic retention time. - - N o data provided by the quoted author. it possible for the Latin Americans to select the most appropriate one, in order to match it to local conditions. Two technical development aspects should be noted. One is that the revised models and the technologies fitting in with the needs of small-scale digesters are usually more easily accepted under the local conditions [45, 47]. The other is that the small-scale high-rate model represents a large potential for further application and the future trends of rural digester process development because of its excellent performance. The first high-rate pilot plant for treating highly diluted manure and domestic wastewater has been working in Colombia with the cooperation of Germany and is reported to exhibit excellent performance [180 182]. High-rate processes have also been widely tested in Latin America. They include anaerobic contact, AF, UASB, as well as RALF, a fixed biomass and packed bed process. Hybrid, EGSB (expanded granular sludge bed) and ftuidized bed processes have been reported recently. Among these processes, four have been in full-scale application (UASB, AF, R A L F and anaerobic contact). The earliest investigation into high-rate processes appears to have taken place in 1978 in Cuba for agro-industrial wastes, including stillage [I 83]. The fields of application lie almost always in agro-industry and urban sewage. The UASB process is the most widely investigated and applied high-rate process. In Latin America, it was proved to be economic and technically feasible for the treatment of both concentrated wastewater (15 g COD/l) such as stillage, and diluted wastewater (0.5 g COD/l) such as domestic sewage [142]. Besides, a kind of "simplified technology" of UASB was reported and design criteria were investigated and proposed [184]. The RALF process was developed in the State of Parana, Brazil, for municipal sewage treatment [90, 911. Full-scale digesters are already commercialized. Present reports show that there are 18 suppliers of this technology in Brazil. Five of them utilize technology licensed in Europe. The locally developed technology represents 68% of the number of digesters commercialized and 53% of the digesters' total volume in the industrial sector [65]. In most situations of the rural areas in Latin America, the first purpose of biogas technology implementation is obtaining energy. In some cases in urban sectors, energy generation is also the first objective [90]. In the industrial

sector, biogas generation offers additional interests to the enterprises that intend to adopt pollution removal technologies. Technically, the biogas generation efficiency is one of the important priorities. Some of the efficiencies obtained in Latin America are listed in Table 6. Because of the favourable ambient temperature, in the full-scale field application, the biogas generation rate from the digesters without heating is better than in many other regions. 4.2. Biogas treatment and end-use There are reports available about biogas treatment technologies in Latin America [79, 108, 117, 118, 124, 187 198]. However, when biogas is produced in small quantities, treatment is usually not considered, because it is uneconomic. Two cases of large-scale biogas treatment have been reported. One concerns biogas produced from sewage treatment [79, 89]. The other concerns landfill gas. Three of the five exploited landfills are reported using biogas treatment technologies. The purpose of biogas treatment is chiefly H 2S and/or CO 2 removal. The technologies used for H :S removal are steel wool filters and water scrubbing; whereas that for CO2 removal are water scrubbing, the Selexon process or selective membranes. The most complete system of landfill gas treatment is found in the C E M I G landfill in Belo Horizonte city, Brazil. The abstracted biogas contains 96% of methane after three stages of cleaning: de-sulphurizing using steel turnings, scrubbing with city water, and a pressure swing molecular sieve for final gas clean-up (Fig. 7). Various kinds of biogas end-uses have been reported in Latin America. In different sectors these end-uses are not the same. In rural areas, the biogas produced is usually used for cooking and lighting. Employment in drying, cooling, tractor fuel and power generation is also reported. In the industrial sector, the main uses now are vehicle fuel and boiler fuel; electricity generation is also reported. Biogas produced from municipal sewage works and sanitary landfills has been successfully employed as town gas, vehicle fuel and for industrial use including metal cutting and heat treatment. Large quantities of biogas used as vehicle fuel is a unique aspect in the Latin American experience. On the other hand, none of the exploited landfill gas projects uses biogas to generate electricity ; this is a major difference from the landfill projects in North America and Europe~

Technical Note

771

CEMIG Landfill

.az2~ Vertical & horizontal drains Exhaustors (× 2) De-sulphurising units (X 2) Resevoirs (× 2) Process compressors (X 4) Scrubbing by city water, reducing CO2and H2S Pressure swing molecular sieve Hydraulic horizontal cylinder (54 m 3 )

Domestic heating (Under study)

230 bar compressor , ~ Industrial use

Vehicular tilling station (× 2): No.l: 8 km away, high pressure cylinders No.2: Within the methane clean-up plant

Fig. 7. Flowsheet of the exploitation, treatment and end-use of CEM1G landfill gas (drawn according to ref. [89]).

5. ENERGY ASPECTS OF BIOGAS IN LATIN AMERICA As generally recognized, one of the distinguished characteristics of biogas technology is its multi-benefits. Therefore it is natural that in different situations this technology is implemented with different purposes. This is evident in Latin America since in the cases of industrial and metropolitan centres, the first goal of biogas technology is the removal of pollution. However, the energy value of the biogas produced plays an important rote in the adoption of this technology. At the user's level, this is realized generally in one o f two ways. Firstly, when local conventional energy, especially electricity is not easily accessible, biogas digesters are chosen as devices for producing a kind of high-grade energy [45]. This is particularly true in the rural sector, because this high-grade energy can result in convenience and modernization of daily life [199, 200]. Besides, many other social and ecological benefits derive from the use of biogas, referred to as the qualitative value of biogas. Secondly, compared with other pollution-free technologies when biomethanation is used, a kind of energy (biogas), which represents an additional benefit is produced fsee Fig. 6). When the biogas is properly used as an energy resource and is evaluated in economic terms, a monetary figure is obtained. This represents usuall) an economic advantage, which can be used for quantitative comparisons, and is referred to as the quantitative value of biogas.

Both the qualitative value and the quantitative value contribute to the total energy value of biogas. At the user's level, the value of biogas is viewed qualitatively or quantitatively according to the real situation. At the national level, whether for Latin America or other developing regions, both of them must be taken into account. However, when looking at Latin America as a whole, it is evident that the energy value depends essentially on the amount of biogas produced. The amount of biogas produced yearly in Latin America can be estimated on the basis of some available parameters. For the rural sector, the main parameters are the number of biogas digesters ; the average voIume of individual digesters; digester operability; the number of days in use annually; and biogas production efficiency. For the industrial and municipal sectors, the main parameters are : the total volume of the digesters ; the number of days in use annually; and average efficiency of biogas production. For the landfill gas schemes, data of biogas produced from the four main landfills are readily available. The calculation yields a quantity of biogas produced ann ually of217 million m 3in Latin America, equivalent to 187 000 tonnes ofoil (toe) (Table 7). At the regional level, this figure is negligible. It is only about 0.4 ppm of the total energy consumption of 446 × l0 ~ toe in the whole Latin American region [10]. Nevertheless, the importance of biogas should also be approached from another way. Firstly, renewable energy has a unique strategic significance in the future. In the long term beyond the fossil era, it is becoming increasingly apparent

772

Technical Note Table 7. Amount of annual biogas production in Latin America

Rural digesters Industrial and municipal wastewater digesters Landfill gas schemes Total

that the energy choices are limited to nuclear fission, nuclear fusion, and renewable energy [201]. Even nuclear energy is considered to be definitely not the option for the nineties as most countries using it have had tremendous problems with waste disposal and accidents [202]. Secondly, at the user's level, the biogas produced represents a certain amount of energy resource and can cover a certain percentage of energy demand. In economic terms, the use of the biogas produced can considerably reduce the running costs of pollution removal systems. Therefore, whether this technology is used in the rural sector, the industrial sector or the municipal sector, many Latin American countries consider that it has a great energy as well as economic importance [89, 150, 203-205]. Some cases of biogas production and use provide convincible evidence. The normal operation of a rural digester can produce 0.17 0.40 m 3 biogas/m 3 digester per day with a methane content of 55-60% [44]. Therefore, a digester of I0 m 3can provide daily 1.7~4 m 3 biogas to the family or 33 570 78 980 kJ of energy, substituting an important part of, or even all of, the energy needs for domestic use. In the treatment of stillage, based on research results in Argentina, it is expected that the production of a full-scale plant would cover 65 70% of the energy demands for the distillery [204]. Calculation indicates that around 30% of the biogas produced, after treatment to 96% CH4, can replace the diesel used by the tractors and trucks on the farm. The remaining 70% can be employed, without any treatment, to replace part of the bagasse burned to generate steam in the distillery [205]. In municipal sewage treatment, at the station in Piral do Sul, Parana State, Brazil, 31 576 m 3 of biogas were produced to supply 286 homes for domestic use from March 1984 until January 1985 [90, 91]. Another station in Silo Paulo, Brazil, with a nominal capacity of 6000 Nm 3 per day is in operation to supply 200 service vehicles after biogas upgrading [79, 89]. The energy aspect of landfill gas is even more impressive. In Rio de Janeiro, Brazil, 253 vehicles including 100 city taxis are running with upgraded biogas, using 78 000 m 3 monthly [153]. From the La Feria landfill in Santiago, Chile, about 9000 m3/h landfill gas is extracted. Some 7500 m3/h are used in the town gas plant, increasing the production of the plant by 20% [150, 176].

Annual biogas production (million m 3)

Tonnes of oil equivalent (thousand toe)

3.4 126

2.9 108

88 217

76 186

Technical improvement is always indispensable since all applications of the biogas technology are intrinsically the exploitation of its technical advantages. Adapting low-cost, high-efficiency processes from the other regions to the condition of Latin American users is necessary. However, the locally developed technologies can often better suit the particular local situations. Even for the readily imported technologies, improvement and modification are necessary. Technological priorities should be taken into account. A good technology should be cost-effective. But in the rural sector, development of different technical levels of digesters should be aimed at in order to meet the need of both poor and well-off rural families. Moreover, integrated resource recovery systems can improve the financial viability of biogas plants and help to combine several goals into effective programmes. Therefore, it is necessary to develop its use in different sectors. The end-use of biogas is sometimes not actually emphasized, when the first purpose of this technology is pollution removal. This is also a technological weak point which is worth improving. Another important necessity is the favourable implementation circumstances which need more positive political and administrative support. As it is frequently noted [89, 93, 153, 203, 206], the use of biogas and biogas technology is not strongly encouraged in some of the Latin American countries. An obvious example is the energy prices. Whereas the price of petrol fuel and ethanol is subsidized by the state, the cost of biogas is paid totally by its producer and user. Thus, although biogas can provide more energy, environmental, social and ecological benefits, it is placed in an unequal position of competition with other sources of energy. Another example is the insufficient budget for R & D into biogas technology. In the field of landfill gas exploitation, this is the main cause of retarding the launch of new landfill gas projects, although some of them have long been planned. Finally, the existing biogas programmes and projects should be reinforced and relative adjustment of implementation strategies made. For the demonstration projects, the qualitative goal is more important than the quantitative one. The former can be expressed as the real acceptance of the technology by the adopter. Obviously, this will need to take into account all the energy, economic and social factors that influence the adoption of biogas technology.

6. FUTURE R & D R E Q U I R E M E N T S Although biogas R & D has reached remarkable achievements in Latin America, some technological, economic, political and sociological difficulties are still met. The future efforts should aim at solving these problems and at pushing forward the present achievements.

7. CONCLUSION Biogas exploitation as a renewable energy in Latin America has its own characteristics. In some of the application fields, Latin America is playing a leading role in the world or among the developing nations. This makes the Latin

773

Technical Note American experience a precious part of the world's experience in biogas technology. From a global point of view, the quantity of biogas produced in Latin America is still very small. But at the user's level, the biogas produced represents an important part of energy and economic value. At the national level, its social, environmental and ecological benefits are also very positive. However, some difficulties still exist. Further R & D of biogas in Latin America will need multiple efforts, not only technological research but also the work of the various types of government and non-government institutions in order to create more favourable circumstances for the exploitation of this renewable energy.

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105.

Technical Note

Seminar/Workshop Anaerobic Treatment of Sewage. Amherst, MA, U.S.A. (Edited by M. S. Switzenbaum), pp. 277 305 ([985). H. A. Bollmann and M. M. Aisse, The experience o[" Paran~Brazil, on Small and Medium Scale Sewage Treatment, pp. I 12. ISAM, Pontifical Catholic University of Parana, Brazil (1991). A. J. Torres, P. P. V. Pereira and A. C. F. Pereira, Potentials of the upflow anaerobic biodigestion process for domestic sewage treatment. In: Poster-Abstracts. Sixth Int. Svmp. on Anaerobic Digestion. S6o Paulo, Brazil, p. 60 (19913. N. L. R. Nucci, G. E. O. Giacaglia, P. A. Nobre, M. E. Souza, S. M. M. Vieira, A. M, Craveiro and I. C. Gomes, Anaerobic treatment research, development and perspectives in the Stfite of Sao Paulo, Brazil. In : Proc. o f the Seminar~Workshop Anaerobic Treatment o f Sewage. Amherst, MA, U.S.A. (Edited by M. S. Switzenbaum), pp. 307-350 (1985). M. H. W. Reis and S. S. M. Vieira, Treatment of domestic sewage by an anaerobic hybrid reactor. In: Poster-Abstracts. Sixth Int. Symp. on Anaerobic D(qestion. Silo Paulo, Brazil, p. 68 (1991). S. M. M. Vieira, Tratamento de esgotos pot digestores anaer6bios de fluxo ascendente. Revista D A E 44, 322 328 (19843. K. B. Pedersen, Production ~f Methane Using an Anaerobic Filter, pp. 1 23. Recinto Universitario de Mayaquez, Universidad de P. R. Puerto Rico (19783. R . A . Barbosa and G. L. Sant'Anna, Treatment of raw domestic sewage in an UASB reactor. Water Res. 23, 1483 1490 (19893. A. Schellinkhout and C. J. Collazos, Full scale application of the UASB technology for sewage treatment. In: Paper preprints. Sixth Int. Symp. on Anaerobic Digestion. S6o Paulo, Brazil, pp. 145 -152 (1991). L. R. Wildschut and G.-J. U. Tovar, Anaerobic treatment of domestic wastewater, full-scale application of the UASB-technology. In : Poster-Abstracts. Sixth Int. Symp. on Anaerobic Digestion. S~o Paulo, Brazil, p. 71 (1991). J. M. Restrepo, Hourly analysis on the performance of a multiple-stage-anaerobic-composite-system for treatment of domestic sewage. In: Poster-Abstracts. Sixth Int. Symp. on Anaerobic' Digestion. Silo Paulo, Brazil, p. 69 (I991). M. Vinas and C. Lopez, Feasibility of the UASB process for the treatment of C u b a n raw domestic sewage. In: Poster-Abstracts. Sixth Int. Symp. on Anaerobic Digestion. S~o Paulo, Brazil, p. 170 (1991). S. M. M. Vieira and P. Alem Sobrinho, Resultados de opera~;~o c recomenda~6es para o projeto de sistemas de decanto-digestor e filtro anaer6bio para o tratamento de sanit~rios. Revista DAE44, 51 57 (1983). J. Duran, P. Bonelli, L. Curcio, P. Della Rocca, M. R. T a m m a r o and S. Tosi, Biodigestores anaer6bicos de flujo ascendente para la depuraci6n de liquido cloacal. In: Cuarta Reuni6n Tbcnica sobre el Desarrollo Tecnoh)gico y Tecnol6gicas Apropiadas para el Saneamiento, Buenos Aires, Argentina, pp. 1 17 (1989). A n o n y m o u s , Digest6o anaerObia de residuos, pp. 1 35. lnstituto de Pesquisas Tecnol6gicas do Estado de S~,o Paulo S/A-IPT, Brazil (1980). A n o n y m o u s , I S A M Em~ironmentaI Sanitation Institute, pp. 1 5. Pontifical Catholic University of Parana, Brazil (19913.

106. A. W. Albino de Souza, A. B. d'Oliveira, J. A. dos Reis, W. Safiotti, C. Laluce and S. Massaro, Digestor anaer6bico para lixo, esgoto e outros dejetos. In : SimpOsio Nacional sobre Fontes Novas e Renov~veis de Energia, Brasilia, 1986, pp. 103 104. Minist~rio das Minas e Energia, Secretaria Geral, Secretaria de Tecnologia (1988). 107. H. A. Bollmann, M. M. Aisse and C. S. Gomes, A experi6ncia paranaense de tratamento de esgotos em pequena e m6dia escale. In: BraziL Europa Seminar on Energy from Biomass and Waste, pp. 1 35. Belo Horizonte, Brazil (1988). 108. E. B. Camargo, Aproveitamento do metano do gdls de esgoto em veiculos, pp. 1-13. C o m p a n h i a de Saneamiento B~isico do Estado de Silo Paulo-SABESP, Brasil (1983). 109. J. L, Carvalho, M. E. Souza and S. M. M. Vieira, Studies for reducing the start-up time of UASB reactors treating domestic sewage. In: Poster-Abstraets. Sixth Int. Symp. on Anaerobic D~qestion. S~to Paulo, Brazil, p. 56 (1991). 110. T. M. T. Gasi, C. E. M. Pacheco, L. A. V. Amaral and S. M. M. Vieira, Removal of pathogenic microorganisms from UASB reactor effluent by chlorination. In: Fi[?h Int. Symp. on Anaerobic Digestion. Bologna, Italy (Edited by E. R. Hall and P. N. Hobson), pp. 875-878. Pergamon Press, Oxford (1988). 111. T. M. T. Gasi, S. M. M. Vieira and C. E. M. Pacheco, Resultados preliminares de cloraqfio de efluente de digestor anaer6bio de fluxo ascendente tratando esgotos dom~sticos, ln: 14' Congresso Brasileiro de Engenharia Sanit(tria e Ambiental. S~o Paulo, Brazil (1987). 112. G. E. O. Giacaglia, Aproveitamento energ6tico de residuos urbanos. In: Encontro Tkcnico sobre Tecnologia de Bioghs. lnstituto de Engenharia/COMGAS, Silo Paulo (1985). 113. G. E. O. Giacaglia, Tratamento anaer6bio de esgoto sanit{lrio. In : P A L E S T R A SABESP, Sao Paulo (1985). 114. G. E. O. Giacaglia, Projeto tkenico de uma usina de aproveriamento energPtico de lixo e esgoto urbano. C O M G A S , S~o Paulo (19843. 115. G. E. O. Giacaglia and I. T. S. Gogolevsky, Aproveitamento integrado de residuos urbanos, pp. l 72. Brasconsult, Engenharia de Projetos LTDA. S~o Paulo (1984). 116. C. S. Gomes, Modulos de tratamento anaer6bico de esgotos dom6sticos com processamento de gfis para fins automotivos. In : Anais do 12' Congresso Brasileiro de Engenharia Sanitbria e Ambiental, Vol. 2, Resumos dos Trabalhos Tkcnicos, p. 112. Associa~fio Brasileira de Engenharia Sanitfiria e Ambiental-ABES Balne~rio Camboriu, S.C. (19833. 117. C. S. Gomes, Tratamiento de desagues con la tecnologia tipo flujo ascendente UASB, ejectuado por la Sanepar, Brasil, incluyendose la digesti6n solida de basura, y la producci6n y utilizaci6n del biogas. In: Seminario Nacional sobre Tecnologia UA SB para Aguas Residuales Dombsticas e Industriales. Cali, Colombia (1984). 118. C. S. Gomes, UASB type treatment of domestic industrial waste waters by S A N E P A R - B R A Z I L including dry anaerobic digestion and biogas production utilization. In: Seminario sobre Tratamiento Anerobio de Aguas Residuals, pp. 1 46. Cali, Colombia (19843. I19. C. S. Gomes, Tratamiento de aguas residuales

Technical Note dom6sticasfindustriales con el tratamiento UASB ej~cutado pot SANEPAR-BRASIL incluyendo digesti6n anaer6bica seca con producci6n y utilizaci6n de biogas. In: Seminario sobre Tratamiento Anerobio de Aguas Residuals, pp. 1-110. Cali, Colombia (1984 i. 120. M. R. La Igiesia, Recuperaqio da energia produzida nos esgotos. In: Seminhrio National de Produ~6o de Energia por Bioconvers~o-Digest6o Anaer6bia, pp. 1 19. Campina Grande (1983). 121. G. Lettinga, A. de Man, P. Grin and L. Hulshoff, Anaerobic waste water treatment as an appropriate technology for developing countries. Trib. Cebedeau 519,21 32 (1987). 122. J. Louwe Kooijmans, G. Lettinga and G. R. Parra, The UASB process for domestic wastewater treatment in developing countries. J. Institution Water Engineers Scientists 39, 437~451 (1985). 123. J. Louwe Kooijmans and E. M. van Velsen, Application of the UASB process for treatment of domestic sewage under sub-tropical conditions, the Cali case. In : Anaerobic Treatment : A Grown-Up Technology. Proc. Water Treatment Conf. Amsterdam, Netherlands, pp. 423~436 (1986). 124. M. J. Nielsen, Utilizaqfio do gfis metano proventente da purificaq~.o do gas de esgoto. IIa Parte. EnergiaFontes Alternativas 5, 2(~27 (1983). 125. C. A. Nobre and M. O. Guimarfies, Experimentos em digestfio anaer6bia de esgotos urbanos. Revista DAE 47, 75 85 (1987). 126. R. F. V. Novaes, C. M, Rech, M. G. Figueiredo and L. A. Giaj-Levra, Bacterial identification of granular sludge from domestic sewage USAB-reactor. In : Fifth Int. Syrup. on Anaerobic Digestion. Bologna, Italy. (Edited by E. R. Hall and P. N. Hobson), pp. 61~4. Pergamon Press, Oxford (1988). 127. R. F. V. Novaes and C. M. Rech, Estudos sobre granulaqio bacteriana em reatores anaer6bios de fluxo ascendente operando corn esgotos dom~sticos. Revista DAE46, 194~195 (1986). 128. N. L. R. Nucci, Estudos de aplica~fio de filtro anaer6bio de fluxo horizontal ao tratamento de esgotos municipais. In: Relatbrio Convenio Sabesp-Cetesb. Silo Paulo, Brazil (1973~). 129. U. Pawlowsky, Tratamiento de aguas residuales dom6sticas alternativas. In 2nd Seminar in Wastewater Treatment. ACODAL, Bogota_, Colombia (1983). 130. M. E. Souza and P. Alem, Estudos da tratabilidade d~ esgotos e lodos de (~reas altamente industrializadas, pp. I 167. CETESB, Brazil (1980). 13 I. M. E. Souza and A. D. Garcia Jr, Utiliza~io de digeslores anaer6bios de fluxo ascendente para o tratamento de vinhoto. Revista DAE46, 200-201 (1986). 132. M. E. Souza, S. M. M. Vieira, C. H. Catabi and W. Borba, Demonstraq~o em escala real da tecnologia de tratamento de esgotos dom6sticos por digestor anaer6bio de fluxo ascendente. Primeiros resultados. In : 14 Congresso Brasileiro de Engenharia Sanithria e Ambiental. Silo Paulo, Brazil (1987). 133. S. M. M. Vieira and M. E. Souza, Development of technology for the use of the UASB reactor in domestic sewage treatment. Water Sci. Technol. 18, 109-121 (1986). 134. S. M. M. Vieira, C. E. M. Pacheco, P. C. A. Nobre. J. C. Vilela and M. E. Souza, Modification of Imhofftank to UASB reactor for sewage treatment. In: PosterAbstracts. Sixth Int. Symp. on Anaerobic Digestion. S6o Paulo, Brazil, p. 70 (1991).

777

135. S. M. M. Vieira and A. D. Garcia Jr, Sewage treatment by UASB-reactor. Operation results and recommendations for design and utilization. In: Paper preprints, Sixth Int. Syrup. on Anaerobic Digestion. Sdo Paulo, Brazil, pp. 133-144 (1991). 136. S. M. M. Vieira, M. E. Souza, J. L. Carvalho, A. D. Garcia Jr, C. E. M. Pacheco, C. H. Catabi and W. Borba, Tratamento de esgotos por digestfio anaer6bia. Ambiente 1, 132 137 (1987). 137. S. M. M. Vieira, C. E. M. Pacheco and M. E. Souza, Efeito da variagio de razfio em digestor anaer6bio de fluxo ascendente tratando esgoto domestico. In: 14 C~mgresso Brasileiro de Engenharia Sanitaria e Ambiental. Sa6 Paulo, Brazil (1987). 138. L. R. Wildschut, Postratamiento del efluente de un reactor UASB tratando desechos dom6sticos. In : Seminario Nacional Sobre Tecnologia UASB para Aguas Residuales Domksticas e lndustriales. Universidad del Valle, Cali, Colombia (1984). 139. Anonymous, Anaerobic treatment and re-use of domestic wastewater--pilot plant study. Cali, Colombia. HASKONING, Royal Dutch Consulting Engineers and Architects, Nijmegen, the Netherlands; Agricultural University of Wageningen, the Netherlands; Universidad del Valle, Cali, Colombia ; INCOL, lngenieros Consultores LTDA, Cali, Colombia, 146 pp. (1985). 140. Anonymous, Tratamiento anaer6bico y reuso de aguas residuales dom6sticas-estudio planta de prueba, Call, Colombia. HASKONING, Royal Dutch Consulting Engineers and Architects, Nijmegen, the Netherlands ; Agricultural University of Wageningen, the Netherlands ; Universidad del Valle, Cali, Colombia ; INCOL, Ingenieros Consultores LTDA, Cali, Colombia, 107 pp. (1986). 14l. A. Schellinkhout, Resultados de la planta piloto en Cali, Marzo 1983-Septiembre 1984. In: Seminario sobre Tratamiento Anaerobio de Aguas Residuales. Universidad del Valle, Cali, Colombia (1984). 142. A. Schellinkhout, G. Lettinga, L, van Velsen, J. Louwe Kooijmans and G. Rodriquez, The application of the UASB-reactor for the direct treatment of domestic waste water under tropical conditions. In: Seminario sobre Tratamiento Anaerobio de Aguas Residuales. Cali, Colombia, pp. 259 276 (1984). 143. A. Schellinkhout, F. F. G. M. Jakma and G. E. Forero, Sewage treatment: the anaerobic way is advancing in Colombia. In: Proc. F!fth Int. Symp. on Anaerobic Digestion. Bologna, Italy. (Edited by E. R. Hall and P. N. Hobson), pp. 767 770 (1988). 144. A, Gendebien, M. Pauwels, M. Constant, M.-J. LedrutDamanet, J. Butson, H. C. Willumsen, R. Fabry, G.L. Ferrero, H. Naveau and E.-J. Nyns, Landfill Gas ." from Environment to Energy. Office for Official Publications of the European Communities, Luxembourg, pp. 1 865 (1992). 145. Anonymous, Cost Benefit Analysis of Landfill Gas Utilization in Developing Countries, pp. 1-20. Hisan, Sao Pauto, Brazil for World Bank (1986). 146. Anonymous, Prospects in Developing Countries ./or Energy .from Urban Solid Wastes, pp. 1-24. Office of Energy, US Agency for Int. Development (1988). 147. Anonymous, Landfill gas for China. Quant. J. Renewable Energy 7, 1(~17 (1989). 148. G. E. Blight, J. M. Ball and J. J. Blight, Moisture distribution in sanitary landfills. In : Proc. Sardina 91,

778

Technical Note

Third Int. Landfill Syrup. Cagliari, Italy, pp. 813-822 (1991). 149. S. Deboosere, P. Van Meenen, D. Boetin, R. Sudrajat and W. Verstraete, Potential for biomethanation of solid wastes in developing countries. M I R C E N J. 4, 29-36 (1988). 150. F. Galvez, G. Fernandez and V. Casas-Cordero, Santiago Chile builds recovery system. Sun Worm 7, 115, 126 (1983). 151. J. J. Lee, H. S. Shin, W. B. Lee and H. Chung, Simulation of leachate quality using lab-lysimeter. In : Proc. Sardina 91, Third Int. Landfill Symp. Cagliari, Italy, pp. 865-875 (1991). 152. T. M. Letcher, R. Schiitte, B. La Trobe and R. Theron, Experiment relating to the exploitation of methane from a small landfill serving 80,000 people. In: Proc. Sardina 91, Third Int. Landfill Syrup. Cagliari, Italy, pp. 451-463 (1991). 153. J. H. Penido Monteiro, Landfill gas recovery--an important alternative energy resource for developing countries. In: Proc. Sardina 91, Third Int. Landfill Syrup. Cayliari, Italy, pp. 431--449 (1991). 154. F. A. Raimundo and S. B. H. Pinto, Gas de aterro sanit~trios. Review Limpeza Publica 10, 3 (1978). 155. S. Robena Jr, Current solid waste management activities in Puerto Rico. In: Gas and Leachatefrom Landfills: Formation, Collection and Treatment. (Edited by E. J. Genetelli and J. Cirello), pp. 18-26. Report No. EPA-600/9-76-004, U.S. EPA, Cincinnati, OH (1975). 156. W. Schmidell Netto, C O M G A S vai produzir metano por digest~.o anaer6bica do lixo. Quimiea e Derivados 124, 27-28, 33 (1976). 157. W. Schmidell Netto, P r o d u ~ o de energia do lixo. Revista Brasileira de Engenharia Quimica 2, 6-10 (1978). 158. C. Xianwen and Z. Yanhua, Landfill gas utilization in China. In : Proc. Sardina 91, Third Int. Landfill Syrup. Cagliari, Italy, pp. 491-503 (1991). 159. Anonymous, A energia que vem do lixo. CETESB J. 35, 2 (1979). 160. Anonymous, Sistema piloto para a recupera¢gto e capta~to de g(~s em aterro sanit~rio, la fase de amplia~o proieto de pesquisa e de desenvolvimento de tecnologia, relat6riofinal. Companhia Estadual de Gfi.s do Rio de Janeiro, Brazil (1980). 161. Anonymous, Aproveitamento de bioghs nos aterros sanithrios do munieipio de $6o Paulo---Experi~ncias da COMGA S e perspectivas de utiliza¢6o, 1-36. COMGAS, S~.o Paulo, Brazil (1985). 162. R. Fernandes, Lixo urbano: de foco de doen~as a o b t e n ~ o de combustiveis. Revista Funda~o Jones dos Santos Neves 3, 38 (1980). 163. A. G. Ferreira, G~is de aterros sanit~trios. Atualidades do Conselho Nacional do Petr6leo 10, I1 14 (1978). 164. I. C. Gomes, G~is de aterro; a energia recuperada do lixo. Energia--Fontes Alternativas 2, 24-30 (1980). 165. I. C. Gomes, G~.s de aterros sanitfi.rios: o projeto da COMGAS. Atualidades do Conselho Nacional do Petr6/eo 12, 60q56 (1980). 166. L. M. Q. Lima, Landfill methanogenesis : a case study of Campinas Town (Brazil). Comp~ndio de Publica¢6es, Companhia Paulista de Forf.a e Luz I!, 81-95 (1985). 167. L. M. Q. Lima, Metanog~nese em aterros--uma retrospectiva hist6rica. Comp~ndio de Publicaf6es, Companhia Paulista de For~a e Luz II, 1-22 (1985). 168. F. A. Raimundo and S. B. H. Pinto, Aproveitamento do gfis de aterro sani~rios. In : Trabalhos Apresentados--

Semin{trio sobre Energia de Biomassas. S6o Paulo, Brasil, pp. 166-188. Instituto Brasileiro do G~s, Rio de Janeiro (1978). 169. K. C. Shin, Abfallentsorgung in Rio de Janeiro. Miill und Abfal121, 20~214 (1989). 170. R. Silveira, A experi~ncia da Companhia Estadual de G~ts do Rio de Janeiro no aproveitamento do g~s produzido a partir de rejeitos urbanos. In : Congresso Brasileiro de Energia, 1°, pp. 7 17. Companhia Estadual de Gas do Rio de Janeiro, Rio de Janeiro (1978). 171. R. Silveira, Alternativas de mat6ria-prima para a produqfio de g~is combustivel no Rio de Janeiro. Revista Brasileira de Engenharia Quimica 4, 5 9 (1980). 172. E. L. Straus, Groundwater monitoring : considerations about laboratory limitations. In: Proc. Sardinia 91, Third Int. Landfill Symp. Cagliari, Italy, pp. 1255 1267 (1991). 173. M. A. Veit and W. Zulauf, Brazil landfill gas potential. Worm Bank Data (1982). 174. M. A. Veit, W. Zulauf and K. Stuermer, Extraction and utilization of landfill gas in Brazil. In : The Third Int. Symp. on Anaerobic Digestion. Boston, U.S.A. pp. 227-250 (1983). 175. W. E. Zulauf, G. Bantel, J. R. L. Machado and G. A. Oliva, G~s de lixo--projeto Elbas. In: Energia, 1 Seminhrio de Energia da Associa~'~o Brasileira de Metais. Volta Redonda, R J, Brasil, pp. 39 59. Comissfio T6cnica de E n e r g i a ~ O E N G E (1980). 176. C. L. Leci, Landfill gas as a town's gas extender, the Santiago Chile experience. In : Landfill Gas and Anaerobic Digestion of Solid Waste. Chester, U.K. (Edited by Y. R. Alston and G. E. Richards), pp. 162-188. Harwell Lab., Atomic Energy Authority, U.K. (1989). 177. T. Kessler, Brazilian trends in landfill gas exploitation. In : Int. Con.[. on Landfill Gas : Energy and Environment '90 (Abstr.). Bournemouth, England, I0.I. (1990). 178. P. F. Bente Jr (Ed), The Bio-eneryy Directory. The BioEnergy Council, Washington, D.C. (1980). 179. Y. S. Hirata and A. M. Craveiro, Estfi.gio de desenvolvimento e applicaq~o da digestfio anaer6bia no Brasil. In: Brazil-Europa Seminar on Energy from Biomass and Waste. Belo Horizonte, Brazil, 1 14 (1988). 180. M. Esguerra, Practical Experiences with Low-cost Biodigesters for the Generation o[" Energy and the Treatment of Sewage in Developing Countries, pp. 1 12. Dipl. Wirtschaftsing. Berlin (1989). 181. N. Hees, Diffusion of biogas plants in the Valle del Cauca, Colombia. Biogas Forum 40, 17 (1990). 182. R. Kloss, High-rate plants for anaerobic treatment of wastewater and production of biogas. Biogas Forum 44, 4-13 (1991). 183. G. Rodriguez, Tecnologia UASB para los desechos de la industria fermentativa. In : Seminario National sobre Tecnologia UASB para Aguas Residuales Dombsticas e lndustriales. Cali, Colombia, pp. 1 35 (1984). 184. M. E. Souza, Criteria for the utilization, design and operation of UASB reactors. Water Sci. Technol. 18, 55-69 (1986). 185. A. M. Craveiro, H. M. Soares and W. Schmidell, Technical aspects and cost estimations for anaerobic systems treating vinasse and brewery/soft drink wastewaters. Water Sci. Technol. 18, 124-134 (1986). 186. J. F. Calzada and C. Rolz, Anaerobic digestion in the integrated utilization of coffee wastes. In : Proc. of Third Int. Syrup. on Anaerobic Digestion. Boston, Massachusetts, U.S.A. pp. 315 324 (1983).

Technical Note 187. Anonymous, No sertfio da Paraiba gfis do esterco de vaca jfi faz motor de fusca funcionar. Interior 6, 4- 13 ([980). 188. Anonymous, Construa um biodigestor e obtenha o gfis para cozinhar, iluminar, e acionar motores. Ponteiro 4, 8 9 (1980). 189. Anonymous, Estudo de alternativas de utilizaf~o de biogZJs produzido, como matkria-prirna para a indhstria quimica, pp. 1 22. lnstituto de Pesquisas Tecnoldgicas do Estado de Silo Paulo S/A-IPT, Brazil (1982). 190. Anonymous, Adaptacibn del motor de gasolina para el jimcionamiento con biogas, pp. 1 7. Cartago, Centro de Energia, Instituto Tecnoldgico de Costa Rica (ITCR) (1983). [91. E. Alvarez Asch, Utilizacion de metano en motores de combustidn interna. Tesis hlg. Mec. Universidad Eacultad de Ingenieria, San Jos6, Costa Rica (1979). [92. E. Alvarcz Asch and C. B. Alvarez, Utilisacidn de metano en motores de combustidn interna.--lI. Univcrsidad de Costa Rica, San Jose (1980). 193. L. C. Beduschi, A. R. Ortolani, O. Coan and L. R. Lopes, [Jso do trator a biogfis em um sistema energ6tico integrado (Urea proposta de pesquisa). In: Sirnp('~sio National sohre Fontes Novas e Renova~eLs' de Enerqia. Brasilia, 1986, pp. 246 249. Minist6rio das Minas e Energia, Secretaria GerM, Secretaria de Tecnologia (1988). 194. S. C. Gomes, Biogasification installations for producing hydrogen or methane. Chem. Abstr. 98. 260 (1983). 195. A. M. Martinez and P. Muk-is del Pozo, Research on biogas and utilization in isolated rural communities. In : Fuel Gas Production./?om Biomass (Edited by D. L. Wise), pp. 121 134. CRC Press, U.S.A. (1981). 196. W. Nori and M. Forjaz, Biogfis para motores estacionfirios. Recista de Quimica lnduslria! 50, 14 ( 1981 ).

779

197. K. Rischbieter and R. Quintero, Utilizaci6n de biogas en motores y equipo de combustion. In: Manual de Biogas, pp. 273 301. OLADE, CEMAT, Guatemala (1981). 198. M. Tay Oroxom, Sistemas de purificacidn de biogas y su uso en equipos rflsticos y cocinas de alta eficiencia. Manual de Biogas, pp. 247 272. OLADE, CEMAT, Guatemala (1981). [99. L. Sasse, Methodology and criteria for the evaluation of biogas programmes. In: Biogas Technologies and Implementation Strategies. Proc. Int. Can/~ Pune, New Delhi, India, pp. 127 [46. BORDA, Germany (1990). 200. J. Hohlfeld, L. Sasse and C. Zimmermann, Production and Utilization q/Biogas in Rural Areas ~['bMustrialized and Dereloping Countries. Deutsche Gesellschafl ffir Technische Zusammenarbeit (GTZ) GmbH, Eschborn (1985). 2(11. W. W. S. Charters, Solar energy, current status and future prospects. Energy Policy 19, 738 741 (1991). 202. A. A. M. Sayigh, Press release, World Renewable Energy Congress. Renewable Energy I, [61 ( 199 l). 203. J. F. Calzada, A. Ricardo, R. A. Garcia, C. A. Porres and C. E. Rolz, Integrated utilization of coffee processing by-products and wastes. In: lnt. Bio.~:vstems (Edited by D. L. Wise), Vol. II, pp. 41 51. CRC Press, U.S.A. (1989). 204. F. Sineriz, Report on the use of biomethanation in Argentina. M I R C E N J . 4, 143 149 (1988). 205. A. M. Craveiro, B. B. M. Rocha and W. Schmidell, Anaerobic digestion of vinasse in high-rate reactors. In: Anaerobic Treatment: A Grown-up Technology. Water Treatment Con/i, A Q U A T E C H "86, pp. 307 319. Amsterdam, The Netherlands (1986). 206. A. Salerno, Biomethanation in Brazil Alcohol Programme. M 1 R C E N J . 4, 135- 138 (1988).