Dear Leo,

I long ago accepted that eating meat wasn't for me. It was mainly the issue of animal welfare that convinced me to shun meat in my diet, but I also agree with the concerns about meat's environmental impacts. However, I worry whenever I hear concerns expressed about the environmental impact of replacement protein such as tofu, of which I now eat a fair quantity. How does tofu compare to, say, an equivalent portion of pork or chicken?

Teri P, by email

Somewhat inevitably this subject tends to quickly slip into the standard "meat eater vs veggie" debate. But wading through the inevitable emotions, there are some strands that most people seem to agree on. Perhaps the most obvious is that growing crops to feed to animals that are then slaughtered and eaten is not the most efficient way for humans to consume their protein requirements.

In terms of reducing greenhouse gas emissions, it would be better if we were to substitute animal products wherever possible with crop-based proteins such as lentils and chickpeas. But things get a little murkier, it seems, when meat substitutes such as Quorn (a factory-produced fungus known as mycoprotein) and soya-based tofu are thrown into the equation.

The recent publication of a report called "How Low Can We Go?", conducted for WWF-UK and the Food Climate Research Network by a research team at Cranfield University, Murphy-Bokern Konzepte and Ecometrica, appears to have stirred up this debate even further. The report aimed to "re-examine total food chain emissions [in the UK] taking into account emissions arising from agriculturally induced land use change". It examined what emissions reductions might be achievable if our diets switched from a largely meat-based diet to one in which substitute proteins such as tofu and chick peas were far more prominent.

It warned of thinking that soya-based products such as tofu were automatically the low emissions answer, though:

"Our analysis shows that direct substitution of livestock products in the diet with analogue high protein products based on for example soy involves increased dependence on imported crop commodities. Such a strategy is likely to increase the total soy intake of the UK food chain. Modern diets have protein in excess and substitution through a general increase in crop products [such as lentils and chick peas] is a more effective and sustainable strategy."

Looks like the hippies were right after all. Lentils and chickpeas are the pulse-based future. The snag, though – there's always a snag – is that we can't readily grow lentils or chickpeas here in the UK:



"Some substitute crops required are currently only grown overseas (e.g. soy, chickpea, lentils). The land required for all these crops to replace beef and lamb is about 1,352 kilohectares (kha), compared with about 135 kha to supply concentrates for ruminant meat now. So, the substitution of beef and sheep meat with Quorn, tofu and pulses clearly demands more overseas land. Part of this is because two major crops selected for substitution are low yielding (lentils and chickpeas at <= 1 t/ha). Were higher yielding pulses used, this demand would clearly be reduced."

As vegetarians and vegans have long realised, a meat-free diet can often mean relying heavily on foods imported from abroad. But the report does seem to conclude that, even knowing that meat substitutes such as tofu and Quorn are a less efficient option than lentils and chickpeas, it is still worth pursuing a meat-free diet if emissions reductions are our goal:

Diet provides single [emissions reduction] measures with big effects. In addition, these measures are technically feasible now. The most effective single measure (meat-free diet) gives a 20% reduction. The benefit of a vegetarian diet increases to about 38% when our estimates of LUC [land use change] emissions are included, but this excludes the loss of soil carbon if UK grassland was converted to arable cropping. Our analysis of the effects of the production of substitutes leads to the conclusion that a broad reduction in livestock product consumption balanced by broad-based increases in crop product intake [such as lentils and chick peas] is a more feasible measure which avoids the land use burden associated with soy based livestock product analogues.

It was a shame in a way that Mildmay's comment below was deleted by the moderators. It would have been interesting to hear back from him as he claimed to be a representative from Quorn and was saying that one of the authors of the report had subsequently admitted that the report's finding on Quorn were based on inaccurate assumptions. My understanding from the moderators is the report's author wrote in to deny ever having said this and, as a result, asked for Mildmay's comment to be removed, as ultimately happened. I asked for both parties to clarify their positions, but, to date, have not had a response.

I also sought some evidence from Mildmay to support his claims that Quorn had a far lower impact than meat, but again, to date, I haven't heard anything back. (There's still time. Please do post below if you are reading this.) What I have found, though, is a reference to a Quorn-commissioned report by De Montfort University's Institute of Energy and Sustainable Development which "early results" show Quorn mince having at least a third less embedded carbon than beef mince. We can only await the final report with interest, I suppose.

There have been plenty of other interesting comments posted below – as always, thank you for taking the time to contribute. As a whole, I would concur with Vegout that the report's conclusions have been somewhat misinterpreted to conclude that by eating less meat it would automatically mean soy-based products being the only alternative and, therefore, result in an increase in deforestation…

Livestock products directly account for nearly two-thirds of food greenhouse gas emissions while providing less than a third of food energy. The report shows that reducing livestock consumption offers the most effective way of reducing the carbon footprint of our food consumption. Removing meat from the diet and replacing it with plant foods with similar protein contents reduces the carbon footprint of diet by one fifth. Replacing all animal products remove nearly a third. The best way to help the environment is to eat less meat and dairy products, this included meat eaters and vegetarians. If food plays a full part in moving to a low carbon economy, these reductions meat and dairy products need to be combined with other measures, including improvements to farming.

As is so often the case, a synthesis of all the views below is probably the best guide to the true picture, but I think Vegout has got to the meat of the matter.

On 16 February, Leo originally wrote

There is unlikely to ever be a meal, or ingredient, that we can confidently claim to be environmentally benign – unless you delight in freeganism. This argument is all about relative impacts, and there does seem to be growing evidence – including a study last week by WWF and Cranfield University – that soy-based proteins such as tofu can have a far larger impact on the environment than we might have otherwise imagined.

As is the format with this series, I will return later this week to discuss the topic in-depth. In the meantime, it would be great if contributors can kick the debate off with their own thoughts below.