Bad Energy? The truth about bioenergy crops

20th Oct 20 by Martin Bowman, Senior Policy and Campaigns Manager

There's no good reason to grow bioenergy crops for “green gas” – let’s grow delicious food, plant trees and build better renewables instead.

This is the second in a series of blog posts exploring the findings of our new report Bad Energy.

The UK’s food security has never been a higher priority – with Brexit looming, the question of how we’ll ensure we become less reliant on imports for what we eat has become a key question. The climate and biodiversity crises means we urgently need to reverse decades of deforestation and start restoring woodlands and habitats to draw down carbon from the atmosphere and create space for nature to regenerate – but whilst also ensuring everyone is fed. In this context, it seems mad to use valuable land to grow crops to burn them for energy. Anaerobic digestion (AD) – the process of producing “biogas” from organic matter like crops and wastes – has presented itself as the silver bullet to everything from producing green gas for heating and transport, to producing fertiliser for our crops. In this second part of our series on AD, we turn to the purpose-grown “bioenergy” crops which are grown especially for AD, and show that they have no role to play in a sustainable future.

Bioenergy crops, like maize and grass, are currently the most controversial feedstock processed by AD plants. The Soil Association has previously highlighted that 75% of sites with late harvested maize used for AD showed high or severe levels of soil erosion – concluding that maize has a “singularly harmful impact” on soils. Nearly a third of maize grown in England is grown as a bioenergy crop for AD. Our report shows that there are far better uses of land than bioenergy crops from almost every perspective. From the perspective of energy generation, we found that solar PV generates 12–18 times more energy per hectare than maize or grass grown for AD.

The AD industry aims to expand bioenergy crops to cover 282,900 hectares – this land could instead be used to grow enough peas to feed 1 million people per year. Grown in rotation, planting vining peas would be much better for soils than maize. Growing peas would also contribute to the UK’s vital shift away from meat intensive diets to eating more plant-based proteins. So from the perspective of food security and soil health, it makes more sense to use valuable cropland to grow food to feed people. The AD industry claims that land spared by preventing food waste could be freed up for bioenergy crops – but this would be a disaster, since this land too would be better used for planting trees, growing plant-based proteins, or for solar PV energy generation.

Growing grass as a bioenergy crop is particularly bad use of land – generating very little energy per hectare, and covering a large area resulting in indirect land use change. Grasses used for AD are often monocrop grasses grown on land which usually requires lots of synthetic fertiliser. Grass leys can increase soil carbon in depleted soils, although long-rotation perennial crops and forests do this more effectively. We found that planting trees saves 11.5 times more emissions per hectare than growing grass as a bioenergy crop, even in today’s context where energy from AD displaces some fossil fuels. In a net zero context, where we have transitioned to more renewables in our energy mix, using grass to feed AD plants actually causes net positive (extra) emissions, not savings:

You can also see from the above that growing maize for AD results in very low emissions savings per tonne by the net zero context. Since we will need to urgently shift to other renewable energy sources like wind and solar to avoid climate crisis, we will need to shift to this net zero context as soon as possible. Subsidies to AD would, therefore, be far better spent on alternatives. From every perspective – energy generation, food production or emissions mitigation – there are better alternative to bioenergy crops. Rather than locking in green gas, we need to focus on faster electrification of heat and transport wherever possible. A recent report found that the UK’s Heavy Goods Vehicles could be completely electrified by the 2030s, at an affordable cost of £19.3 billion. Despite this, the UK government continues to subsidise bioenergy crops for AD – albeit at a lower rate than for wastes (like food waste and manure) – paying out millions of pounds a year to some AD plants. These subsidies are generally locked in for 20 years after they are accepted – the only way for most AD plants to remain financially viable. This is a huge problem, as it effectively locks in subsidies for bioenergy crops for decades, despite the fact that their effectiveness at emissions mitigation is likely to drop dramatically during that time as we decarbonise the economy, and is already far worse than other alternatives. Worryingly, it seems like the government are poised to announce a massive increase in support for biomethane from AD plants. It is essential that public money should not go to support bioenergy crops – the government should focus its money on accelerating tree planting, plant-based proteins and solar PV construction, so that we all have enough to eat in a world safe from climate crisis. A better future demands it.


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