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End of an era
The back pages Almost the last word Is rinsing tomatoes under the tap enough to wash anything harmful off them?
Beef with tofu From an environmental perspective, is it better to eat imported foods like tofu, quinoa and sweet potato or beef from the farm a few kilometres up the road?
Ann Bliss London, UK From an environmental point of view, meat from any source is definitely a non-starter (or main). 54 | New Scientist | 17 August 2019
HERO IMAGES/GETTY
George Monbiot Oxford, UK This question is easy to resolve. In a paper in Nature last year, a team led by Timothy Searchinger of Princeton University examined the impact of various foodstuffs in terms of carbon. This shows that protein from beef is 73 times worse than protein from soya. A kilogram of beef protein has the equivalent carbon emissions of a passenger flying from London to New York and back. The overall carbon cost of 1 kilogram of beef protein is equivalent to 1250 kg of CO₂. Aircraft emissions for longhaul flights are roughly 110 grams per passenger per kilometre, and the return distance is 11,170 km – so 1229 kg of CO₂. In discussing the carbon costs of food, we have greatly exaggerated the role of transport and greatly downplayed the impacts of land use. With the exception of food that is flown, transport tends to constitute a small proportion of the total carbon cost. The crucial environmental task is minimising the area used by farming. Beef is a highly inefficient use of land. Soya, grown in prime sites, is a very efficient use of land – though not without its own major problems. It is also worth noting that there might be more soya in your steak than in your slab of tofu, as the great majority of the world’s soya is grown for animal feed, and conversion efficiencies (especially when producing beef) ensure that you need to pump far more protein into an animal than you get out. So even if you want to eat less soya, you should eat soya.
Clean limbs
This week’s new questions Fresh fruit Most fruit and vegetables sold in supermarkets come with a label saying “wash before eating”. What are the risks of eating unwashed produce and does a quick sluice under the tap reduce them significantly? Ian Cairns, Seaford, East Sussex, UK End of an era Dinosaurs went extinct 66 million years ago, apparently as a result of an asteroid impact. How much time elapsed between that event and the death of the very last dinosaur? Sami Franssila, Helsinki, Finland
The question was asked by someone in Suffolk in the UK. There happens to be a quinoa grower there, as well as others around the country. I stopped eating imported quinoa when I found out that the cost of this staple had gone up prohibitively for the Peruvians because it was being exported to Europe. Swedes can be substituted for sweet potato. As for tofu, soya beans are grown in Norfolk in the UK and go into tofu sold in outlets in Norwich as well as online. We don’t have to make compromises. Just buy locally grown, seasonal foods. You won’t go hungry. Michael Le Page London, UK A lot of people think local is better, but this isn’t true for producing meat and often even for crops. When crops are grown in heated greenhouses with extra lighting, the carbon dioxide emissions can be several times higher than those from transporting the produce
thousands of miles. So-called vertical or indoor farming, which is promoted as being local and eco‑friendly, is especially bad because it typically relies on artificial lighting. Proponents say the lights can be powered by renewable energy. But this would require an area of solar panels at least 10 times larger than that to grow the crop. Louis Albright of Cornell University in New York has worked out that lettuce grown outdoors in California and taken by road, rail or plane to New York has a carbon footprint of 0.7 kilograms per kilogram of lettuce on average. For lettuce grown locally in heated greenhouses with supplemental lighting it is 2.4 kg. And for lettuce grown entirely under artificial light it is 8 kg.
There has been much speculation on Twitter recently about whether we should wash our legs when in the shower. I think legs don’t specifically need washing, and I suspect we overwash generally. How often should we wash, for health benefits or other reasons? (continued)
Hillary Judd Exeter, Devon, UK The question implies that the water running down the legs from the rest of the body while showering is sufficient to wash them. But observation suggests that water runs down in rivulets, leaving areas of unremoved sweat, skin cells and grime. Drying such an area with a towel might not be looked upon favourably by anyone who has to do the laundry. When preparing walls for redecoration, the advice is to wash from the bottom up as dirty water from the higher portions will be more easily removed from a clean surface. Perhaps the same idea should be applied in the shower. Lisa Prickett Newick, East Sussex, UK Previous respondents were male and made good arguments against leg washing in the shower to use as little soap as possible, unless you are a gardener. To add a different perspective, there are many women, and some men (particularly keen cyclists), who shave their legs daily in the shower. Applying a foaming agent or soap helps to reduce irritation and avoid missed strips. Although washing isn’t the primary purpose, in this situation they do get washed daily. ❚
Want to send us a question or answer?
Email us at [email protected] Questions should be about everyday science phenomena Full terms and conditions at newscientist.com/lw-terms
Beef with tofu From an environmental perspective, is it better to eat imported foods like tofu, quinoa and sweet potato or beef from the farm a few kilometres up the road?
Ann Bliss London, UK From an environmental point of view, meat from any source is definitely a non-starter (or main). 54 | New Scientist | 17 August 2019
HERO IMAGES/GETTY
George Monbiot Oxford, UK This question is easy to resolve. In a paper in Nature last year, a team led by Timothy Searchinger of Princeton University examined the impact of various foodstuffs in terms of carbon. This shows that protein from beef is 73 times worse than protein from soya. A kilogram of beef protein has the equivalent carbon emissions of a passenger flying from London to New York and back. The overall carbon cost of 1 kilogram of beef protein is equivalent to 1250 kg of CO₂. Aircraft emissions for longhaul flights are roughly 110 grams per passenger per kilometre, and the return distance is 11,170 km – so 1229 kg of CO₂. In discussing the carbon costs of food, we have greatly exaggerated the role of transport and greatly downplayed the impacts of land use. With the exception of food that is flown, transport tends to constitute a small proportion of the total carbon cost. The crucial environmental task is minimising the area used by farming. Beef is a highly inefficient use of land. Soya, grown in prime sites, is a very efficient use of land – though not without its own major problems. It is also worth noting that there might be more soya in your steak than in your slab of tofu, as the great majority of the world’s soya is grown for animal feed, and conversion efficiencies (especially when producing beef) ensure that you need to pump far more protein into an animal than you get out. So even if you want to eat less soya, you should eat soya.
Clean limbs
This week’s new questions Fresh fruit Most fruit and vegetables sold in supermarkets come with a label saying “wash before eating”. What are the risks of eating unwashed produce and does a quick sluice under the tap reduce them significantly? Ian Cairns, Seaford, East Sussex, UK End of an era Dinosaurs went extinct 66 million years ago, apparently as a result of an asteroid impact. How much time elapsed between that event and the death of the very last dinosaur? Sami Franssila, Helsinki, Finland
The question was asked by someone in Suffolk in the UK. There happens to be a quinoa grower there, as well as others around the country. I stopped eating imported quinoa when I found out that the cost of this staple had gone up prohibitively for the Peruvians because it was being exported to Europe. Swedes can be substituted for sweet potato. As for tofu, soya beans are grown in Norfolk in the UK and go into tofu sold in outlets in Norwich as well as online. We don’t have to make compromises. Just buy locally grown, seasonal foods. You won’t go hungry. Michael Le Page London, UK A lot of people think local is better, but this isn’t true for producing meat and often even for crops. When crops are grown in heated greenhouses with extra lighting, the carbon dioxide emissions can be several times higher than those from transporting the produce
thousands of miles. So-called vertical or indoor farming, which is promoted as being local and eco‑friendly, is especially bad because it typically relies on artificial lighting. Proponents say the lights can be powered by renewable energy. But this would require an area of solar panels at least 10 times larger than that to grow the crop. Louis Albright of Cornell University in New York has worked out that lettuce grown outdoors in California and taken by road, rail or plane to New York has a carbon footprint of 0.7 kilograms per kilogram of lettuce on average. For lettuce grown locally in heated greenhouses with supplemental lighting it is 2.4 kg. And for lettuce grown entirely under artificial light it is 8 kg.
There has been much speculation on Twitter recently about whether we should wash our legs when in the shower. I think legs don’t specifically need washing, and I suspect we overwash generally. How often should we wash, for health benefits or other reasons? (continued)
Hillary Judd Exeter, Devon, UK The question implies that the water running down the legs from the rest of the body while showering is sufficient to wash them. But observation suggests that water runs down in rivulets, leaving areas of unremoved sweat, skin cells and grime. Drying such an area with a towel might not be looked upon favourably by anyone who has to do the laundry. When preparing walls for redecoration, the advice is to wash from the bottom up as dirty water from the higher portions will be more easily removed from a clean surface. Perhaps the same idea should be applied in the shower. Lisa Prickett Newick, East Sussex, UK Previous respondents were male and made good arguments against leg washing in the shower to use as little soap as possible, unless you are a gardener. To add a different perspective, there are many women, and some men (particularly keen cyclists), who shave their legs daily in the shower. Applying a foaming agent or soap helps to reduce irritation and avoid missed strips. Although washing isn’t the primary purpose, in this situation they do get washed daily. ❚
Want to send us a question or answer?
Email us at [email protected] Questions should be about everyday science phenomena Full terms and conditions at newscientist.com/lw-terms