Food and Carbon Capture

Ecosystems are complex, and if we want to change ours, or rather avoid what we have being changed too much by our activities, we have to make some trade offs amongst some of the energy sources and sinks in the mix, and avoid what may seem to be easy short cuts.  For example, some look to using food waste as an energy source. It sounds sensible, since the waste already exits, but Feedback research carried out with help from Bangor University says that to cut emissions most we need to cut food waste not recycle it as energy. 

Feedback’s report ‘Bad Energy’ claims that preventing food waste results in direct emissions savings of over nine times higher than from processing it into biogas via anaerobic digestion (AD)- basically letting it rot in a confined space thus producing methane gas.  And afforestation on the roughly 3 million hectares of grassland that would be spared if we could halve UK food waste, would save and offset about 11.3% of the UK's current total greenhouse gas emissions.  

No to AD!  

So the AD bio-methane route was a delusion. That’s very surprising: one of the AD industry's claimed benefits is that it provides a sustainable solution to food waste, by turning it into renewable energy. But Carina Millstone, executive director of Feedback, says: ‘Our findings make clear that AD is not the climate solution we need—it is a distraction at best, and a dangerous hindrance at worst’. 

Feedback also seems to broaden the critique beyond food to include biomass grown as energy crops for biogas production. That is a more familiar complaint: energy crops compete directly with food production, whereas food waste already exists. But perhaps it shouldn’t, or at least should be reduced. And Feedback evidently feel the same way about some animal framing and its wastes- and emissions. They worry that AD subsidies may ‘actively facilitate the expansion of intensive livestock farming, through lowering the costs of waste disposal and helping factory farms obtain planning permission’. Thus ‘AD risks perpetuating and expanding the very polluting industry whose environmental effects it proposes to mitigate’.

More generally they say that, ‘far from only dealing with ‘unavoidable waste’, when AD subsidies are set very high, as the AD industry is calling for, AD can actively hinder waste prevention, particularly when paired with a lack of regulation and funding for the better alternatives. Companies and redistribution charities have reported that edible food can be diverted down the food waste hierarchy to AD when incentives are skewed towards AD, hindering prevention efforts. Government funding for food waste prevention has been cut over the last decade, while AD has been heavily subsidised.’

So overall they are pretty unhappy with AD. They say ‘AD does have a ‘sustainable niche’, but it is much smaller than the role the industry envisages for itself. As a destination for food waste that cannot be prevented or sent to animal feed, AD can be preferable to landfill. It also mitigates manure and slurry emissions where meat and dairy are produced within a sustainable food system, for example as part of a mixed, regenerative and nutritionally optimised agricultural system’. 

Otherwise though they seem to see most AD as undesirable, with support for it ‘crowding out better environmental alternatives’. For example, it claims that solar PV generates 12–18 times more energy per hectare than maize or grass grown for AD.  And that planting trees saves 2.6 times (maize) and 11.5 times (grass) more emissions per hectare than growing bioenergy crops for AD.  And it also says that dietary shifts to more plant-based diets would have significantly greater emissions mitigations potential than using manures and slurries as AD feedstocks.  Controversial stuff!

Carbon capture   

Some other related controversies have also emerged.  For example, a current view is that Biomass with Carbon Capture (BECCS) is vital to cut CO2 levels.  Biomass can be burn to generate energy and the CO2 released can be captured and stored so that, if new biomass is replanted, the whole cycle is carbon negative. However, large areas of land would have to be used to grow biomass to make much impact on CO2 levels. Direct Air Capture (DAC) might be better – and it can be done anywhere and without the need for biomass.  But it is an energy using process, and like BECCS, it would need large CO2 storage areas. Arguably, trees do the same job and are easier to deploy!

A useful article in Grist takes a look at some of the land/water food/energy trade offs between these various CO2 capture routes. Grist notes that a study by Jay Fuhrman et al found that direct air capture could ‘soften the blow’ of biofuels, when it came to land use, but ‘even with prompt action to get to net-zero emissions, the level of BECCS and reforestation needed to hold global warming to 1.5 degrees C by the end of the century could still cause food prices to double or triple around the world by 2050, and get even higher in the Global South’. Their model ‘showed that water use would still go up dramatically as well, because so many direct air capture facilities would need to be built that it would cancel out the water benefits of growing fewer bioenergy crops. And the energy required to power these carbon-sucking machines would be monumental: It would be equivalent to more than all of the natural gas the world consumes today.’ 

Wouldn’t it be easier to avoid all this and just expand renewables more and faster? Or do we have to do both? As I have argued before, there is the risk that too much of a focus on carbon capture will delay the rapid development of renewables- the only sustainable way to avoid emissions on the supply side.  If we do have to capture some CO2, why not go for reforestation- which, unlike BECCS or DACs, also has other wider ecological benefits?  Trees may not be a perfect or permanent carbon sink and they do take up land, and food growing area. But so do all the other options to a greater or lesser extent, as well, with BECCS and DECs, as CO2 storage space.  We have to decide on the best food/land/energy/carbon compromise and artificial carbon removal may not be viable on a large scale.  

These trade offs are not easy. For example, in its new 2030 climate plan the European Commission has tried to tip the balance in favour of protecting carbon sinks and forestry. It says that ‘any unsustainable intensification of forest harvesting for bioenergy purposes should be avoided,’ and ‘the use of whole trees and food and feed crops for energy production - produced in the EU or imported - should be minimised’, in order to limit the impact on climate and biodiversity. However, Euractiv reports that bioenergy producers have disputed the EC view, saying that ‘active forest management’ practices can ‘optimise the carbon flow’ and promote carbon sinks. The debate goes on!