Reducing life cycle fossil energy and greenhouse gas emissions for Midwest swine production systems

Journal of Cleaner Production xxx (xxxx) xxx

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Reducing life cycle fossil energy and greenhouse gas emissions for Midwest swine production systems Joel Tallaksen a, *, Lee Johnston a, b, Kirsten Sharpe a, Michael Reese a, Eric Buchanan a a b

West Central Research and Outreach Center, University of Minnesota, Morris, MN, 56267, USA Department of Animal Science, University of Minnesota, St. Paul, MN, 55108, USA

a r t i c l e i n f o

a b s t r a c t

Article history: Received 2 January 2019 Received in revised form 17 May 2019 Accepted 21 October 2019 Available online xxx

Over the last 30 years, the US swine industry has concentrated more animals on fewer farms in the Midwest US corn-belt region to more efficiently produce pork. At the same time, the food industry is beginning to be called upon by consumers to supply products with lower environmental footprints. Swine producers have opportunities to decrease the environmental impacts of their products, but need to know where the most beneficial changes can be incorporated. This study examined the fossil energy consumption and global warming potential (GWP) emissions at Midwestern swine farms using life cycle assessment methodology. Cradle-to-gate swine production scenarios were modeled using a combination of farm productivity survey data and on-farm energy monitoring, with an emphasis on activities related to swine production facilities and their operations. Fossil energy use totaled 10.6 MJ per kg of hog live weight (LW) in the average commercial scenario, 67% of which was used in the grow-finish stage, 11% in the farrowing stage, 12% in the nursery stage, 6% in gestation and 4% in gilt development. Average commercial scenario GWP emissions were 2.41 kg CO2 equiv. per kg hog LW, with 75% emitted during the grow-finish phase, 6% in farrowing, 9% in the nursery phase, 7% in gestation, and 2% in gilt development. Fossil energy required and GWP emissions for facilities and operations were 3.36 MJ and 0.15 kg CO2 per kg hog LW, respectively, and accounted for 32% of the system fossil energy and 6% of emissions in the average commercial scenario. Though fossil energy and GWP impacts resulting from swine production facilities and operations are smaller than those for feed ingredients and manure management, swine producers can directly influence these impacts through management. Heating, cooling, and ventilation are prime areas in facilities and operations where energy efficiency technology could reduce impacts. Lowering facility and operation energy inputs by 30% would decrease fossil fuel use in the system by 10% and slightly decrease GWP emissions. In the future, substituting renewable energy for fossil-based energy and using other efficiency technologies for current electricity and heating fuel needs may be able to eliminate the fossil energy needed for swine facilities and production operations. © 2019 Elsevier Ltd. All rights reserved.

Handling editor: Giovanni Baiocchi Keywords: Swine LCA Fossil energy Greenhouse gas Life cycle assessment Livestock

1. Introduction The US is a major producer and exporter of pork and generates roughly $20 billion dollars worth of pork per year, with the number of animals produced rising over the last decade (Adair et al., 2016; Stalder, 2017; USDA-ERS, 2017; USDA-NASS, 2012). Changes in the swine industry have concentrated more animals on fewer farms in the Midwest US corn belt region, where a combination of climate and ready access to feed grains optimizes swine production

* Corresponding author. E-mail address: [email protected] (J. Tallaksen).

economics. At the same time, environmental impacts of swine production are becoming better documented and more completely understood. Commonly observed, regionally relevant impacts include fossil fuel depletion, greenhouse gas emissions, eutrophication of waterways, water use, and decreased air quality due to noxious odors (Hansen et al., 2014; Webb et al., 2014). As the consequences of these environmental issues become better understood, the food industry is being called upon by consumers and some nations/regions to supply products with lower environmental footprints (Gowdy and Winston, 2016). However, the food processing/packaging and retail industry is somewhat limited in its ability to directly reduce impacts of agricultural based products. Their

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traditional role restricts them to improving efficiencies in their directly controlled processing/packaging and delivery systems. The on-farm production of commodities used for food processing and retail sales is a significantly larger component of the environmental impacts of food production (Thoma et al., 2011, 2013). Therefore, the food industry is beginning to look towards crop and livestock producers to help improve the environmental footprint of the food supply chain. This is especially true with livestock, poultry, and milk production; because they are at the top of the agricultural food chain, consuming grain and other agricultural-based feedstocks. Three areas of pork production systems account for most of the environmental impacts of pork production: crop and feed production, manure management, and the facilities and operations activities needed for animal husbandry (McAuliffe et al., 2016). A number of researchers have attempted to optimize the environmental footprint of swine diets by altering feed composition (Cherubini et al., 2015; Garcia-Launay et al., 2014; Reckmann et al., 2016). The primary focus has been on using different blends of starches, proteins, and trace elements to provide a complete diet, while selecting ingredients that have lower environmental impacts (Lamnatou et al., 2016). Unfortunately, the current availability and higher costs of lower impact ingredients limits the likelihood of their adoption. Changes in diet, manure handling, and manure storage have been suggested to reduce manure based environmental impacts (Prapaspongsa et al., 2010). However, the ability to lower manure emissions is limited and it would likely be uneconomical for producers to implement emissions reduction practices. A near-term means for improving the environmental footprint of swine production systems may be to concentrate on reducing fossil energy inputs and the associated greenhouse gas emissions in day-to-day animal husbandry activities. Operation of equipment in the swine production facilities is where producers directly use energy, as opposed to embodied energy used in feed production. To maintain a healthy environment for pigs, constant fan-based, powered ventilation is used for fresh air and cooling in most facilities. Heating is another major energy input, especially in the early stages of swine growth when piglets need to be kept warm. Ventilation and heating equipment is typically powered by electricity, propane or natural gas. These same energy sources are also needed for lighting and generation of hot water for sanitation. In addition to contributing to fossil energy depletion and greenhouse gas production, these energy inputs are costly to producers. Therefore, swine producers have a vested economic interest in reducing energy inputs, which results in lower environmental impacts as well. Life cycle assessment (LCA) methodology has been used to examine environmental impacts of swine production in a wide variety of swine studies world-wide. Previous LCA research on the environmental impacts of commercial scale Midwest swine production incorporated engineering and electrical estimates to broadly examine energy use and greenhouse gas emissions of swine production systems (Gilbert, 2009; Lammers et al., 2012; Pelletier et al., 2010; Stone et al., 2010). Because these studies did not measure actual energy use on operating commercial swine farms and because facilities have grown in size, there is a need to better quantify energy consumption and the related environmental impacts of swine production in the Midwest. This study employed LCA methodology to examine cradle-togate environmental impacts of swine production using on-farm energy data from large, commercial-scale facilities and from smaller niche systems. The potential impacts of deploying energy efficiency measures and alternative technologies to reduce fossil energy and greenhouse gas impacts were also examined. In examining these potential improvements, we focused on a number of small-scale, low-cost changes that may be acceptable to

producers and can reduce energy use in experimental or applied settings. This is in contrast to other studies that have focused on more substantial single issue changes to production systems that would likely not be implemented by producers, even though they showed potential improvements in their environmental impact. The work targeted swine production in the U.S. Midwest region, where cold winters and warm summers significantly influence facility operations and energy loads. 2. Materials and methods The key methods used for this study are described below. Additional methodology and further background information can be found in the supplemental materials, which includes Tables A1A12 and Fig. A1. 2.1. Project goals, scenarios, and data overview The study had several goals; the first and foremost was to determine baseline greenhouse gas emissions and fossil energy use in large-scale Midwestern swine production using current data from commercial farms. It was also important to look at the range of these environmental impacts over a variety of high and low performing systems, as well as at less conventional niche swine production operations. A final objective was to examine the potential for swine producers to reduce greenhouse gas emissions and fossil energy use in their operations. Five different swine production scenarios were examined to meet these objectives (Table 1). The scenarios included different resource use, facilities, and management assumptions to represent likely variations in productivity found in the region. Three commercial system scenarios were modeled: the average (baseline), a high performing, and a low performing scenario. Each scenario combined the average, high, or low energy performance data with the corresponding average, high, or low swine productivity data. Both data types and performance metrics are discussed further below. Some swine producers are also exploring alternatives to the typical large-scale enclosed commercial operations. Often referred to as niche production (Honeyman et al., 2006; Lammers et al., 2007b), these systems produce pork that has certain attributes which are not found in traditional commodity pork. This may include pork that is organic, antibiotic-free, direct market/farm-totable, or pork raised in systems that some consider to be more humane. Two niche production scenarios were included in this study; a conventional system that mostly mirrored current large conventional commercial systems but at scale for specialty production and an alternative niche system that incorporated different farrowing and housing methods. These alternative methods included a deep bed-farrowing system (Li et al., 2010) and hoop barns (Honeyman and Harmon, 2003) for both gestation and growfinish production. Analysis for these systems included only environmental impacts; welfare impact categories may be assessed later as welfare data and impact methods for livestock systems (Müller-Lindenlauf et al., 2010; Renggaman et al., 2015) are further developed. 2.2. LCA scope and boundaries This study uses LCA methodology to examine the overall fossil energy and greenhouse gas impacts associated with each scenario plus areas of interest, or hotspots, which might be targeted in efforts to reduce environmental impacts. In an LCA, the inputs, outputs, and processes of production systems are documented and the environmental impacts of all inputs, outputs, and processes compiled for a summary assessment of a given impact. The LCA

Please cite this article as: Tallaksen, J et al., Reducing life cycle fossil energy and greenhouse gas emissions for Midwest swine production systems, Journal of Cleaner Production, https://doi.org/10.1016/j.jclepro.2019.118998

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Table 1 Swine production scenarios modeled and data sources used The 2016 nationwide swine production survey (Stalder, 2017) provided swine production data for commercial scenarios. Commercial scenarios used on-farm energy data from swine facilities in West Central Minnesota. Niche scenarios used production and energy use data from the University of Minnesota, West Central Research and Outreach Center (WCROC) research farm swine production facility. Production Scenario

Swine Production Survey Data

Energy Data

Commercial Average High Performing Low Performing Niche Conventional Niche Alternative

Survey average for production Top 25th percentile production Bottom 25th percentile production WCROC conventional production WCROC alternative production

The average of commercial facilities The low energy use facility The high energy use facility WCROC conventional WCROC alternative

conducted for this study was a cradle-to-gate, attributional LCA of live weight pork production with an emphasis on the energy inputs into animal husbandry. Pork produced from sows was separated from this analysis using economic allocation at the farrowing stage. The functional unit for the final product of the study was 1 kg of market hog live weight (LW) leaving the farm. Foreground activities in the scenarios analyzed included farrowto-finish activities that are generally under the control of swine producers (Fig. 1). Infrastructure (production facilities and equipment) was not considered. Background activities included production of crops, whose impacts were based on cropping systems at the regional swine facility producing the niche swine. The nutritive energy value of feed (Lammers et al., 2010b) was not tracked during the study. Land use change (direct and indirect) was not considered in assessing ingredient or feed production, nor for facility footprint. 2.3. LCA production scenario construction Modern US swine production practices use multiple farms that each raise pigs through a single production stage. Analyzing individual swine production stages is helpful for the goal of identifying areas where significant environmental impacts are occurring. However, to analyze the impacts for the complete swine production life cycle, scenarios must merge data from all farms in the supply chain needed to raise hogs from birth to farm gate (Fig. 2). Commercial swine production is typically segregated into three farms: breed-to-wean, nursery, and grow-finish. In commercial breed-towean operations, a single farm typically will house the gilt development unit (GDU) for raising replacement breeding stock, the

Fig. 1. LCA overview and boundaries for the swine production system. The schematic shows the foreground (swine production system) and background (production support systems) components of the modeled swine system analyzed.

gestating animals, and the farrowing unit with sows and their piglets. The activities of the commercial breed-to-wean operations were separated in this study to allow a more detailed analysis of each of the production stages. The niche production systems were similarly divided into the five stages analyzed: GDU, gestation, farrowing, nursery, and grow-finish. The three major categories of input data used for constructing the scenarios were herd management and productivity, energy use, and feed data. Of particular interest for this study was the on-farm energy consumption data and the farm-based production management survey data, which were important in examining current commercial production impacts. 2.4. Life cycle inventory The swine life cycle inventory was based on facility data and major feed ingredients (crops grown) sourced within 60 km of Morris, MN (95.78
W, 45.59
N). The 30-year average summer high and low temperatures are 26
C and 15.3
C, while the winter average high and low are 6.8 and 17.7
C, respectively. Annual precipitation is 673 mm, predominately recorded in summer. Regional commercial swine production facilities (Table A1) included a mix of retrofitted older facilities and newer purposebuilt, state of the art swine production equipment. Niche systems included a number of swine research facilities at the University of Minnesota, West Central Research and Outreach Center (WCROC), which were equipped with energy and environmental monitoring equipment. 2.4.1. Energy data collection and calculation On-farm energy consumption data were monitored at six commercial swine production facilities (Sharpe et al., 2018), two for each stage of production (breed-to-wean [GDU, Gestation, Farrowing], nursery, and grow-finish) (Table A1). Niche system energy use data was collected from WCROC for the same stages. Data collected included electricity, heating fuel (propane or natural gas), and diesel fuel use. Animal inventory and building occupancy was also assessed. In all systems, electricity was monitored using data loggers on building energy loads. Because of the large scale of the commercial facilities, electricity data were collected on sub-units of the facilities, which were comprised of many identical rooms with the same heating/ventilation, lighting, and feed delivery systems. Data were then scaled up to represent the entire operation. Wherever possible, electrical circuits were traced to identify the end use of the electricity (i.e. heaters, lighting, and office equipment). Electricity use was calculated based on data from one full year, 2016, to account for seasonal variations in use. Propane was monitored by billed delivery volume and natural gas using billed quantities from commerce grade meters on site. Preliminary efforts that tracked liquid fuels (gasoline and diesel) to move workers or animals, used for back-up generator testing, and manure handling equipment at WCROC showed relatively small amounts of energy

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Data Sources

Stage

GDU

Gilt Development Impacts

On-Farm Energy Use On-Farm Energy Use

Farrowing

Swine System Impacts

Farrowing Impacts

On-Farm Energy Use

Nursery

Nursery Impacts

On-Farm Energy Use

Grow-Finish

Grow Finish Impacts

On-Farm Energy Use

Fig. 2. Data and stages used in developing swine production scenarios. On-farm energy use and national production survey data were combined to model impacts at each stage. System impacts were modeled by combining the individual stages.

use and so these were not tracked at commercial operations or used in this analysis. Determining the higher and lower energy performing commercial system for scenarios involved converting energy use for all energy sources (i.e. natural gas, propane, or electricity) into the total MJ of energy per pig per day for the two facilities monitored at each stage of production (Table 2). The facility with the least energy use per pig per day was rated as high performing, and conversely the low performing facility used the most energy per pig per day. The average of the two systems at each stage was used in the average scenario. The LCA analysis used the units of energy per pig per day (i.e. kWh of electricity, M3 of natural gas) for calculation, with the background regional or national data for their associated environmental impacts. Niche production systems were similarly assessed for daily energy per units per pig.

2.4.2. Swine production data Commercial production scenarios used swine performance data (Table 3) from the 2016 National Pork Board survey (Stalder, 2017). The production survey examined swine industry herd management and operational practices, inputs, and outputs. For each data point monitored, it reported national swine system averages and results for systems in the top and bottom 25th percentile using daily gain

or piglets produced as the productivity metric. The top and bottom 25th percentile data were used in the high and low performing commercial LCA scenarios, respectively. Corresponding swine productivity data was collected for the niche systems. 2.4.3. Feed and feed ingredient production The swine diets modeled for all scenarios relied on the diets in the National Swine Nutrition Guide (USPCE, 2010). Commercial diets were based on the specific ingredients and formulation listed in the recommendations (Table A7). The niche system diets followed the recommendations, with minor changes to starch and protein sources (Table A8). Fossil energy and greenhouse gas emissions data for corn and soybean production were calculated from data collected from agricultural activities at the WCROC (Table A9). The embodied fossil energy and greenhouse gas emissions attributed to other grains, nutritional supplements, and additives in feed mixes were found in published literature or databases. Energy values for grinding of corn and mixing of ingredients were taken from Reckmann et al. (2016). 2.4.4. Manure management and emissions Manure emissions were examined for time the manure spent in the swine production system. Downstream emissions of manure

Table 2 Energy use per animal per day for individual stages in each scenario. Conventional Commercial

Breed-to-Wean

Farrowing Electricity Propane Natural Gas Gestationa Electricity Propane Natural Gas Gilt Development Electricity Propane Natural Gas

Niche Systems

High Productivity

Average Productivity

Low Productivity

Conv.

Altern.

kWh kg M3

2.980 0.0103 0.0186

3.460 0.033 0.009

3.940 0.0564 0

1.02 0 0.635

3.06 0 1.90

kWh kg M3

0.157 0.004 0.007

0.173 0.012 0.004

0.1880 0.0203 0

0.110 0 0

0.110 0 0

kWh kg M3

0.421 0.017 0.030

0.471 0.051 0.015

0.521 0.086 0

0.634 0 0.235

0.110 0 0

Nurserya

Electricity Propane Natural Gas

kWh kg M3

0.048 0.017 0

0.0536 0.0137 0.0031

0.0594 0.0103 0.0062

0.0746 0 0.0645

0.0746 0 0.0645

Grow-Finish

Electricity Propane Natural Gas

kWh kg M3

0.0468 0.0109 0

0.0838 0.0092 0

0.1210 0.0075 0

0.191 0 0.0784

0.0329 0 0

a

Gestation and nursery facilities in the niche conventional and niche alternative systems were the same.

Please cite this article as: Tallaksen, J et al., Reducing life cycle fossil energy and greenhouse gas emissions for Midwest swine production systems, Journal of Cleaner Production, https://doi.org/10.1016/j.jclepro.2019.118998

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Table 3 Production assumptions used in scenarios modeled. The stage length and feed consumption (total kg) for each stage are listed. Each stage used multiple feed mixes. Commercial Systems1

Niche Systems

High

Average

Low

Conv.

Altern.

Stage Length (days)

Gilt Development Gestation2 Farrowing Nursery Grow-finish

140.4 109.8 27.5 46.2 110.4

149.2 124.0 29.1 45.2 119.2

158.7 146.1 30.3 44.9 128.7

142.0 111.0 35.0 35.0 112.0

142.0 111.0 35.0 35.0 112.0

Feed Use (kg for stage)

Gilt Development Gestation Farrowing Nursery Grow-finish

340.9 209.2 177.1 30.6 263.3

348.9 236.3 187.4 26.3 270.5

345.9 278.4 195.2 21.9 268.3

320.2 277.0 225.4 29.5 242.7

343.9 277.0 225.4 29.5 260.6

11.1

10.2

9.4

11.0

9.0

Piglets weaned per litter

1-Based on data from (Stalder, 2017). 2-Gestation calculated using litter per year data, which includes all time between farrowings; whether gestating or non-pregnant.

applied to fields and credits for replacement of synthetic fertilizer were not included in the swine system analysis. Manure storage for all commercial conventional facilities was either in open air tanks or in deep pits under slatted floors in buildings. For the niche systems, most indoor facilities used pits under slatted floors, while outdoor systems used solid manure storage. Manure volumes and volatile solids were calculated based on manure characteristics and production data from Lorimor et al. (2004) and ASABE (2005), using the appropriate animal stages and weights as inputs (Section A3.1). Methane emissions were calculated using IPCC tables for given storage methods and temperatures (IPCC et al., 2006). 2.5. Impact assessment
Modeling work was done using SimaPro v8.4 software (Pre Consultants, Netherlands) with some background items from the Ecoinvent version 2.2 (Frischknecht et al., 2005) and US LCI inventories (NREL, 2012). Fossil energy was calculated using the CED version 1.9 method (Frischknecht et al., 2007) with some additions for North American based primary energy sources. Resulting impacts are reported in terms of MJ of primary units of fossil energy resource depletion, which is the actual amount of fossil energy needed to deliver the measured energy to the swine production system as well as the fossil energy consumed in the system. Greenhouse gas emissions were calculated as per the IPCC GWP 100a method (IPCC, 2013) with global warming potential (GWP) emissions expressed as kg CO2 equivalents per functional unit. 2.6. Sensitivity analysis Model assumptions and background data representing likely ranges for major assumptions important to the study goals were tested in a sensitivity analysis using the commercial average scenario. The model assumptions were varied to include both high and low ranges for energy use, stage length, and upstream corn grain fossil energy and GWP. Impacts for bedding use were assessed in a separate sensitivity analysis included in the supplement (Section A3.3). 3. Results The environmental impacts of swine facility and operations related activities, along with the impacts from other activities, were first examined as full production scenarios and then the inputs and impacts broken down for analysis at the level of individual production stages.

3.1. Production scenario differences Fossil energy use for the entire cradle-to-gate commercial average swine production scenario totaled 10.6 MJ per kg of hog LW (Fig. 3A), 67% of which was used in the grow-finish stage, 11% in the farrowing stage, 12% in the nursery stage, 6% in gestation, and 4% in gilt development. The high productivity (9.36 MJ) and low productivity (12.08 MJ) scenarios, consumed 11% less and 14% more energy than the average scenario, respectively. Fossil energy use in niche conventional system was 36% more (14.38 MJ) than the average commercial scenario, while the niche alternative system was 20% more (12.72 MJ). Fossil energy required for feed production in the commercial average scenario was 67.9% (7.10 MJ per kg LW) of the total fossil energy use and varied less than 10% in all scenarios. Fossil energy use for facilities and operations use was 32.1% (3.36 MJ) of the total fossil energy use in the average commercial system, with a range of 23% less (2.57 MJ) and 36% more (4.58 MJ) energy used in the high and low performing systems, respectively. The facilities and operations fossil energy in the niche conventional scenario consumed 108% (6.98 MJ) more fossil energy than needed for facilities and operations in the average commercial scenario, while the niche alternative used 42% more (4.77 MJ). The GWP emissions released in the commercial average scenario were 2.41 kg CO2 equiv. per kg hog LW (Fig. 3B), with 75.2% emitted during the grow-finish phase, 6.1% in farrowing, 9.2% in nursery phases, 7.0% in gestation, and 2.4% in gilt development. The largest GWP emissions component was from manure emissions, which were 64% of emissions in the average commercial scenario. Feed production emissions were the next largest at 30% of total emissions. Relatively little variation was observed among the scenarios in GWP emissions related to the feed or manure. At 6%, the facilities and operations emissions in the average commercial scenario (0.150 kg CO2 eq. per kg LW) were a small component of total GWP emissions. However, they showed considerable variation among scenarios with a 32% reduction (0.103 kg) and 41% increase (0.212 kg) in the high and low productivity scenarios, respectively. The niche alternative system facilities and operations emitted 9% more (0.164 kg) than the commercial average, while the niche conventional scenario emitted 58% more (0.237 kg). 3.2. Facility and operations impacts by stage To further explore which stages and what activities might have the most influence on the environmental impacts of facility and

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A) Fossil energy use per kg hog LW

A) Fossil energy use per kg hog LW

B) Greenhouse gas emissions per kg hog LW

B) Greenhouse gas emissions per kg hog LW

Fig. 4. Facilities and operations related fossil energy use and greenhouse gas emissions. Impacts are per kg of market swine (liveweight) at farm gate, as calculated using the (A) cumulative energy demand or (B) IPPC GWP 100a (2013) methods, respectively. Fig. 3. Fossil energy use and greenhouse gas emissions. Impacts are per kg of market swine (live weight [LW]) at farm gate for facilities and operations, feed system, and manure systems, as calculated by (A) the cumulative energy demand or (B) IPPC GWP 100a (2013) methods.

operation systems, the data were further broken down by production stages. 3.2.1. Breed-to-wean stages The GDU phase is a longer production stage in comparison to others, but is a relatively small component (7% of total fossil energy) of the resulting environmental impacts for facilities and operations energy in pork production (Fig. 4A). The largest component of energy use was for ventilation, which accounted for the majority of electrical demands in the on-farm GDU data. The commercial average GDU facility used 0.235 MJ of fossil energy per kg LW swine produced, with a 35% reduction (0.153 MJ) and a 52% increase (0.358 MJ) in the high and low performing scenarios, respectively. The niche conventional GDU facility, an indoor housing system with ventilation fans, used 78% (0.418 MJ) more fossil resources than the commercial average facility, while the more passively ventilated

curtain-sided niche alternative GDU used 84% less fossil energy (0.036 MJ). The resulting GWP emissions were 0.009 kg CO2 eq. per kg hog LW for the average GDU facility (Fig. 4B), which is 8% of the total facilities and operations scenario GWP emissions. The high and low performing GDU systems emitted 27% less (0.008 kg) and 40% more (0.013 kg), respectively. The conventional and alternative niche GDU facilities, respectively had 55% more (0.015 kg) and 77% less (0.002 kg) emissions than the average GDU's facilities and operations. The commercial gestation facilities required a relatively small amount of fossil energy (8% of total for the average scenario) for facilities and operations. Ventilation equipment accounted for the largest energy use in the gestation facilities. Average fossil energy consumption in the commercial gestation phase was 0.285 MJ per kg hog LW. The high performing gestation facility used 45% less energy (0.158 MJ) than the average facility, while the low performing system required 37% more fossil energy (0.390 MJ). The gestation facility used in both niche scenarios was an unheated

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hoop style barn, which required a small amount of energy for maintaining ice-free drinking water. The resulting fossil energy use from niche gestation facilities was 0.102 MJ per kg, which was 64% lower than the commercial average system. Bedding use in this facility will add some impacts to both energy use and GWP emissions. Facilities and operations related GWP emissions for the gestation stage were 8% of total facilities and operations related emissions. The commercial average gestation facility emitted 0.012 kg CO2 eq. per kg LW in this stage, with 33% less emissions (0.008 kg) and 40% more GWP emissions (0.016 kg) in the high and low performing systems, respectively. The niche facility emitted 0.006 kg CO2 eq. per kg hog LW, which was a 49% decrease from the average gestation facility. Facilities and operations fossil energy resource use for swine farrowing was relatively high (26% of total) for this short phase of production. Heat lamp energy use accounted for about 60% of the electrical energy, with additional heating by propane or natural gas. The average commercial farrowing facility used 0.873 MJ per kg of hog LW, with a decrease of 29% (0.617 MJ) and an increase of 36% (1.19 MJ) in the high and low performing scenarios. The similarly equipped niche conventional farrowing facility used 0.359 MJ of energy, which was 59% less than the commercial average facility. The highest fossil energy impact for farrowing systems was for the niche alternative farrowing facility, which used 252% more (3.07 MJ) fossil resources than the commercial average. This alternative deep-bedded, group housing system was included because it is promoted by some for animal welfare reasons. However, it used more natural gas heating fuel and produced fewer weaned pigs than the conventional farrowing system. This facility also required bedding, which added environmental impacts. Global warming potential emissions for the average commercial facility were 0.0489 kg CO2 eq. per kg of hog LW for the farrowing stage, which was 33% of the total facilities and operations related GWP emission. The high and low performance scenarios produced 28% less (0.0350 kg) and 35% (0.066 kg) more emissions, respectively. The niche conventional system had 62% less emissions (0.019 kg) than the average commercial system, while the alternative system had 108% more emissions (0.102 kg). 3.2.2. Nursery Fossil energy use and the related GWP emissions for the nursery stage were somewhat balanced between heating young pigs entering the nursery phase and ventilation/cooling needs as pigs neared the end of this phase. In the commercial average scenario, 17% of the total facilities and operations related fossil energy used per kg LW was in the nursery facility. The average commercial nursery's fossil energy requirement for facilities and operations was 0.584 MJ per kg hog LW with 1% less (0.577 MJ) and 3% (0.630 MJ) more fossil energy use in the high and low performing scenarios, respectively. In the two niche scenarios, which both used the same nursery facility, 103% more fossil energy (1.19 MJ) was used per kg LW compared with the average commercial nursery. The average commercial facility emitted 0.018 kg of CO2 eq. per kg LW, with the higher and lower performing facilities emitting 10% less (0.016 kg) and 12% more (0.020 kg), respectively. The niche facility had 78% more emissions (0.032 kg) than the average commercial system. The GWP emissions for the commercial average nursery facility were around 12% of the total facilities and operations emissions per kg hog LW. 3.2.3. Grow-finish The grow-finish facilities used a relatively small amount of energy per day per animal (Table 2), however, the stage is long. Consequently, most resources put directly into generating weight gain for the final market hog are in the grow-finish facility. The

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largest portion of facilities and operations energy, 41%, is consumed in the grow-finish stage. Fossil energy impacts in the grow-finish system were driven mostly by electricity demands of ventilation and cooling fans. The fossil energy consumption for the average commercial facility in the grow-finish stage was 1.38 MJ per kg LW. The high and low performing commercial grow-finish systems required 23% less (1.07 MJ) and 47% more (2.04 MJ) fossil energy than the average scenario, respectively. The niche conventional grow-finish facility used considerably more fossil energy, 255% (4.91 MJ), than the average commercial grow-finish system. The niche alternative hoop barn facility, which had no power ventilation, had 74% (0.364 MJ) less fossil energy use than the commercial average facility. Global warming potential emission for facilities and operations for the grow-finish stage were 41% of the total facilities and operations emissions, with 0.062 kg CO2 eq. per kg LW in the commercial average system. The higher and lower performing systems had facility emissions that were 41% less (0.037 kg) and 55% more (0.097 kg), respectively, than the commercial average. The niche conventional system had 167% higher emissions (0.166 kg), while the low-input niche alternative had emissions that were 66% lower (0.021 kg) than the commercial average. 3.3. Feed system impacts Total fossil energy use for production of feed grains, supplements and grinding/mixing was relatively consistent across scenarios when analyzed for the entire production system. The average commercial system required 7.10 MJ per kg hog LW for feed with a range that was 6% less (6.69 MJ) to 4% more (7.37 MJ) in the high and low performing scenarios. Feed system fossil energy demand for the niche conventional system was 3% more (7.30 MJ) than the average commercial system, while the niche alternative system required 10% more (7.83 MJ) fossil energy per kg LW. The average commercial system emitted 0.719 kg CO2 per kg hog LW, with a 6% (0.676 kg) decrease and a 4% increase (0.749 kg) in the high and low performing systems, respectively. The niche conventional system emitted 4% more (0.750 kg) than the commercial average, while the niche alternative system had 12% more (0.805 kg) emissions. 3.4. Manure impacts The total GWP impact for manure in the average commercial system was 1.53 kg CO2 eq. emitted per kg hog LW, with an 11% reduction (1.36 kg) in the high performing system and a 13% increase (1.73 kg) in the low performance system. The niche systems both had about 16% less GWP emission than the average system at around 1.29 kg per kg hog LW. 3.5. Sensitivity analysis Facilities and operations energy inputs were tested at three different levels in the sensitivity analysis, a 30% decrease, a 15% decrease, and a 15% increase (Table 4). The tested variations were made to the daily energy needed per animal for all stages. The resulting fossil energy use for the production system varied between 90 and 104% of the baseline value of 10.6 MJ per kg of LW. The GWP emissions ranged from 98% to 101% of the baseline value of 2.41 kg CO2 per kg of LW swine under the three energy consumption rates tested. The length in days of the two most energy intense stages, growfinish and farrowing, were also examined to look at how the time an animal spends in a production stage might impact energy use. The analysis tested only the fossil energy use from facilities and

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Table 4 Swine Production System Sensitivity Analysis. Fossil energy results are in MJ per kg of live weight, with the percentage change from the commercial average in parenthesis. Global warming potential results are kg CO2 eq. per kg live weight, with the results relative to the commercial average in parenthesis. Fossil Energy Energy Inputs Total System Energy Facility/Operation Energy Stage Day Length Grow-finish

30% 9.54 2.33

(90%) (69%)

Farrowing Embodied Grain Energy Corn Grain Global Warming Potential Energy Inputs Total System Energy Facility/Operations Energy Stage Day Length Grow-finish Farrowing Embodied Grain GWP Corn Grain

30% 2.37 0.105

(98%) (70%)

15% 10.0 2.82 10% 10.4 25% 10.4 23% 9.59 15% 2.39 0.127 10% 2.40 25% 2.40 76% 2.05

(95%) (84%) (99%) (98%) (91%)

(99%) (85%) (100%) (99%) (85%)

Average 10.6 3.36 Average 10.6 Average 10.6 Average 10.6 Average 2.41 0.150 Average 2.41 Average 2.41 Average 2.41

(100%) (100%) (100%) (100%) (100%)

(100%) (100%) (100%) (100%) (100%)

15% 11.0 3.86 10% 10.7 25% 10.8 54% 12.9 15% 2.43 0.172 10% 2.42 25% 2.42 19% 2.50

(104%) (115%) (101%) (102%) (122%)

(101%) (115%) (100%) (101%) (104%)

operations during the stage and did not vary feed inputs or manure outputs. The grow-finish stage was varied by 11.9 days (±10%) and the farrowing stage by 7.28 days (±25%). This resulted in fossil energy changes of 1% and 2% in the grow-finish and farrowing stages, respectively. Global warming potential emissions changes were less than 1% in the grow-finish stage and about 1% in the farrowing stage. The background fossil energy and GWP emissions attributed to corn grain were examined to determine how higher or lower corn environmental impacts would affect the swine system results. Sensitivity to input fossil energy for corn production was tested using a 23% decrease and a 54% increase from this study's production model value of 1.94 MJ per kg corn grain, based on values in a review by Kim et al. (2014). The resulting fossil energy use in the swine production system showed a corresponding decrease of 9% and increase of 22%, respectively. Sensitivity of the system to changes in corn grain GWP emissions were tested as well, with a 76% decrease and a 19% increase from the baseline value of 2.10 kg CO2 per kg corn grain. Resulting GWP emissions were 15% lower and 4% higher per kg of hog LW for the swine production system.

and regulation constraints impede their manure management system options. This leaves facilities and operations as the primary area where a swine producer has true flexibility to manage the reductions of fossil energy use and GWP emissions. This research analyzed the facilities and operations aspects of the swine production systems in more detail with the goal of identifying specific areas of energy use that could be targeted for reduction. Rather than using engineering values from building design literature for the equipment and energy use in swine production systems, this study was based on measured energy used in existing swine facilities (Sharpe et al., 2018). The majority of facility and operations energy is used for either heating or cooling/ventilation. In the early stages of growth, heating via heat lamps uses a great deal of electricity in addition to propane or natural gas based heat. As the animals mature, more ventilation and cooling is provided to maintain air quality and animal productivity. In determining where reductions in facilities and operations related environmental impacts can be made, swine producers can focus on stage-specific alternative technologies and management strategies for heating, cooling, and ventilation.

4. Discussion

4.1. Opportunities for improving energy use in specific phases of swine production

The GWP impact findings from this study (2.4 kg CO2 equiv. per kg LW) are similar to a number of other studies (McAuliffe et al., 2016). The relative contribution of the feed system, manure management system, and facilities and operations components of swine production identified in this study were consistent with previous studies. Fewer studies have examined fossil energy use in swine production (Lammers et al., 2010a, 2012) and there seems to be variability in the studies, likely due to methodology and background input differences. In terms of fossil energy, the feed production system uses the largest share of fossil fuels going into swine production, followed by the facilities and operations activities. In terms of GWP, the manure management system and feed system were responsible for most of the greenhouse gas emissions. One of the important reasons for this study was to identify areas where swine producers can directly reduce environmental impacts. Producers often have little control over the fossil energy or emissions from the feed ingredients arriving at their farms. Therefore, they have limited ability to influence feeding system impacts. Though swine producers are in control of manure management systems for their production systems, a number of timing, weather,

A wide variety of research exists on reducing facilities and operations energy in swine production using conservation, alternative technologies, and renewable energy sources. Interest in the topic began during the energy crisis of the late 1970's and re-emerged with higher energy prices in the 2000's (Huhnke, 1981; Randall, 1985). Consistent with this study's results, several prior examinations identified farrowing heating for piglets and ventilation for older pigs as hotspots for natural gas and electricity use (Huhnke, 1981; Lammers et al., 2010a). A number of studies examined alternatives that are appropriate to reduce energy consumption without compromising productivity. In farrowing systems, piglets congregate by the sow's side in the creep space, which is typically heated using 125e250 W electric heat lamps with metal reflectors. The standard 250 W heat lamp bulb, would use 6 kW h per day to maintain 36
C on the floor. However, 175 W bulbs have been found to provide sufficient heat levels and improved animal comfort (Ontario, 2016; Xin et al., 1997). Based on lamp wattage, changing bulbs to a lower wattage can reduce electricity consumption by 30%. Testing of different

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bulbs has found that coatings and reflectors can further influence their efficacy (Davis et al., 2008). Rather than use heat lamps, some producers are using floormounted electric heat mats for piglet creep spaces. There are a number of models already on the market in a variety of materials, sizes, and wattages. Analysis of different mats has shown reduced energy use in all cases, with a range of between 36 and 75% energy savings over using heat lamps (Beshada et al., 2014; Ontario, 2016; Stinn and Xin, 2014). These studies typically found that a 65 W heat mat could replace a 175 W light without impacting piglet mortality or average daily gain. An additional benefit is longer lifespan of the mats compared to more fragile light bulbs. The longer lifespan combined with lowered cost of operations provide a significant economic justification for producers to consider installing heating mats. In the nursery phase, both heating and ventilation energy needs are significant for maintaining swine productivity. One solution to addressing the heating aspect is a reduction of temperatures at night. Johnston et al. (2013) found that a 6
C reduction in building temperatures during a 12 h overnight period lowered heating fuel use by 30% and reduced electrical costs 20%. The only required change for most nursery buildings would be a heating controller with a time of day setback option. Energy efficiency improvements can also be made to ventilation systems used in all stages of swine production. By closely examining air movement needs, ventilation can be tuned to maintain animal comfort and health while using less energy (Harmon et al., 2012). Teitel et al. (2008) found 25e35% less energy was needed in agricultural buildings using variable speed control systems for ventilation fans. Regular maintenance and cleaning practices are also able to increase fan efficiency and reduce costs (Sanford, 2012). Maintaining and replacing fans is often needed due to the heavy wear of swine ventilation systems. Upgrading to more efficient fans during a scheduled replacement would not likely be a major expense for producers looking to decrease energy consumption and costs for facility operations. A key synergistic component to these heating and ventilation technologies is an environmental control system that can effectively regulate fans and heaters (Ontario, 2016). Older control systems often allowed for only two modes, on or off, with limited set point options. Newer equipment has variable levels of operation (Teitel et al., 2008; Zhou and Xin, 1999) and can be controlled based on temperature, humidity, time of day, or other environmental data (Sanford, 2012). Newer commercial facilities are being built with more advanced control equipment. The modest costs of upgrading outdated control systems in existing swine production buildings will likely have a quick payback with the reductions in energy expenses (Miller Publishing, 2008). While these alternatives are likely to reduce environmental impacts, it should be noted that the background environmental impacts of the alternatives are not addressed by the studies examining their energy reductions or by this study. For example, a change from heat lamps to heat mats would increase the use of certain plastics in the swine production system, which may have upstream environmental impacts. However, the limited nature of the equipment, maintenance, or setting changes required for these alternatives suggests that there would be minimal upstream impacts relative to the large reductions in energy for the overall swine systems. Swine producers willing to consider major changes to their operations or those building new facilities could reduce ventilation energy consumption by selecting building designs known to use less energy. Many swine facilities are designed so that power ventilated fans are the only means of moving air in or out and are built so that air flows from one end to the other, which is referred to

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as tunnel ventilation. A more energy efficient design is curtainsided ventilation construction where the open sides of the building are covered by large curtains that can be opened or closed to let wind move fresh air through the facility (Jacobson et al., 2011). In a small sample of Iowa facilities, Hanna et al. (2016) found that curtain sided facilities used 28% less electricity than tunnel ventilated facilities and other work has shown energy savings with comparable pig performance (Stender et al., 2003). Another energy savings option examined in the niche alternative scenario was the hoop barn (Honeyman and Harmon, 2003; Lammers et al., 2007b). These barns are generally tarpaulincovered structures with low wooden walls and open ends that house groups of animals. The open ends allow for natural ventilation, which eliminates the need for ventilation fans. Lammers et al. (2007a) observed a 63% reduction of energy use in hoop based systems compared with conventional housing systems. While these structures require less energy, there are drawbacks. Animals housed in these systems need bedding, and the facilities need periodic manure removal using skid loaders or tractors, both of which increase fossil energy use. Additional feed is typically required when raising animals in hoop barns during cooler months compared to conventional confinement barns (Honeyman and Harmon, 2003). While overall energy use and expense is lower, producers are typically not in favor of this housing option as it introduces more variation in productivity due to changing temperatures, requires more labor, and uses bedding. 4.2. The potential for lower impacts by reductions in facility energy use The energy consumption component of the sensitivity analysis was designed to evaluate the impact of reduced facilities and operations energy use on the overall fossil energy and GWP impacts. Facility energy use reductions of 15% and 30% were examined in the average commercial production scenario. These levels were based loosely on the potential energy efficiency saving for the entire system when implementing the alternative equipment and methods discussed above. A 30% reduction of facilities and operations energy use resulted in a decrease in fossil energy use of 10% for the entire production system. Because manure and cropping systems GWP emissions are much higher than facilities and operations energy related GWP emissions, a 30% reduction in operations energy use resulted in only a 2% decrease in GWP emissions in the swine production system. Swine production facilities that are already high performing from an energy efficiency standpoint, may not be able to reduce energy use by a full 30%, hence a 15% reduction was also examined. The sensitivity analysis suggests a 15% savings in operations input energy yields about a 5% reduction in fossil energy use for the swine production system and roughly a 1% decrease in GWP emissions. Although the results of these changes in facility and operation equipment and management may seem small compared to possible changes in other parts of the system, they are achievable using existing technologies and enhancements. Based on the cost of establishing a commercial swine production facility in the Midwest, the technology changes are relatively inexpensive and can have a rapid return on investment. The direct financial impacts are the most persuasive arguments to convince many Midwestern farmers to upgrade their facilities to enhance sustainability efforts. 4.3. Further reductions or elimination of facility and operations energy impacts With the correct combination of existing technologies, fossil energy and related GWP impacts from the facility and operation

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activities of commercial swine production could be substantially mitigated or even eliminated. This requires transitioning from equipment using fossil-based energy to equipment capable of using renewably produced energy. A good example is geothermal heating/cooling systems. These systems use the ground as a heat source or sink in combination with a heat pump to substitute for the thermal energy of propane or natural gas combustion (Jacobson et al., 2011). While geothermal systems use more electricity than conventional heating systems, they have a much higher energy efficiency per MJ of heating/cooling provided and can use renewable electricity. Similarly, other common fossil energy demands such as hot water and ventilation can be met with renewable technologies such as solar photovoltaic or solar thermal systems (Love and Shah, 2011), wind energy systems, and biogas production (Adair et al., 2016). Anaerobic digestion is a renewable energy production solution that perfectly complements swine systems because it can produce biogas for both heat and electricity generation. However, most producers are not currently considering it due to real or perceived barriers in implementation (EPA, 2015), including technology, economic, regulatory, and operational issues. In the future, economics and improvements in technology may make anaerobic digestion a more appealing option for reducing fossil-based energy. While eliminating fossil energy use in swine production may seem like an unrealistic goal, the economics of renewable energy technologies are improving quickly. At some point, producers may decide to install technologies which reduce or eliminate fossil energy related environmental impacts simply for economic reasons. 5. Conclusion While facilities and operations related fossil energy and GWP impacts are a smaller component of the swine production system than feed and manure related impacts, swine producers can directly improve the environmental performance of their swine production systems and facilities. The majority of impacts result from energy used for heating, cooling, and ventilation. Relatively inexpensive equipment upgrades such as changing climate control systems, switching from heat lamps to heat mats, and more efficient ventilation fans, along with improved operating procedures can be used to lower energy demands in different production stages. The energy efficiency measures needed to reduce fossil energy consumption by 10% will likely have a relatively quick return on investment. Future renewable energy resources or efficiency technologies would further reduce or could even eliminate fossil energy use and related GWP impacts in swine production facilities. Funding statement Funding for this project was provided by the Minnesota Environment and Natural Resources Trust Fund as recommended by the Legislative-Citizen Commission on Minnesota Resources (LCCMR). Acknowledgements The authors would like to thank Anderson Farms, Hillside Hogs, Moore Lean, Moser Farms, and participating producers for their gracious support and for allowing us to conduct energy consumption research in their swine production facilities. Appendix A. Supplementary data Supplementary data to this article can be found online at https://doi.org/10.1016/j.jclepro.2019.118998.

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Please cite this article as: Tallaksen, J et al., Reducing life cycle fossil energy and greenhouse gas emissions for Midwest swine production systems, Journal of Cleaner Production, https://doi.org/10.1016/j.jclepro.2019.118998