Biomass and Other Dubious Renewables

Arianne Shahvisi

When I lived in Beirut, seven years ago, I diligently sorted my household waste and carried it into the university where I worked so I could use the recycling bins on campus. One of my students saw me dropping plastic and cardboard through the different labelled openings and urged me to peer inside. The chutes all ended in the same bin. Last month I learned that much of the plastic I’ve been ‘recycling’ in Brighton over the last five years has been incinerated in Newhaven, producing small amounts of electricity while releasing carbon dioxide and noxious gases.

In 2020, more of the UK’s electricity was generated from renewables than fossil fuels for the first time. But the second largest source of renewable energy in the UK, after wind but well ahead of solar, is biomass, which amounts to the prehistoric practice of burning wood. Biomass is an umbrella term for any organic material that can be used as fuel, which includes wood, food waste, sewage, straw, manure and animal litter. Fossil fuels are also, strictly speaking, very old, geologically metamorphosed biomass. The important difference is that the Intergovernmental Panel on Climate Change classifies biomass as a renewable source of energy, where ‘renewable’ means replenishable over human timescales, as opposed to the millions of years required to turn life into oil or coal.

Most of the biomass burned in British power stations is wood pellets: slugs of compacted sawdust whose combustion is allegedly carbon neutral. Their emissions are comparable to fossil fuels’, but the carbon released by burning wood was captured by photosynthesis relatively recently, and in time a newly planted tree will reabsorb it, bringing the equation neatly back to zero.

Yet it’s possible to cut down, pulverise and burn a tree without planting a replacement, and then we’re one carbon-capturing tree down and the greenhouse effect is one combusted tree up. Using wind to power a turbine does not deplete the future wind supply; turning the energy of incident photons into electrical current does not reduce the amount of sunlight we get. Even if wood pellets are renewable, they won’t necessarily be renewed. That requires the keeping of promises.

Timescales also matter. The release of carbon on combustion is almost instantaneous; reabsorbing it can take decades. A recent study puts the payback time for biofuels at between 40 and 104 years. That might be within a human lifespan, but it’s a bit like hoping to mop up an oil spill by repeatedly shaving your head.

Part of the trouble is the idea that trees are just wood, wood is carbon, and carbon is fungible. Most of the wood pellets burned in the UK are imported from Canada and the United States, where mature forests which underwrite vast, complex ecosystems are being felled to meet the growing European demand for ‘renewable’ energy. The official line is that pellets are made from offcuts from the timber industry, but scientists and environmentalists report that trees are being felled to go straight to biomass.

Worse, the trees that are planted to offset biomass consumption are not forests in an ecologically recognisable sense; they are monoculture industrial plantations of non-native species with no understory, a limited ecosystem, and lower carbon sequestration than the natural forests they are supposed to replace. Not all wood is alike; old growth forests are worth far more than sacks of pellets for electricity generation.

The demand for wood pellets now rivals that for timber, given the incentives offered by European governments pursuing renewable energy agendas. The UK government spends around £1.5 billion a year in biomass electricity subsidies, encouraging the importation of millions of tonnes of minced North American trees as a ‘green’ energy source, more than anywhere else in the world. The Drax power station in North Yorkshire received £800 million in subsidies last year to convert four of its generating units into biomass burners, and promises to wind down coal combustion by 2022, ahead of the 2025 deadline for the UK as a whole.

Biomass is not the only dubious renewable that is powering deforestation. The Indonesian government plans to phase out fossil fuel imports by deriving biofuel from palm oil. The Iceland advert that had us scanning the ingredients of shampoo and peanut butter glossed over this graver threat to the natural habitats of orangutans. An area of high conservation value rainforest as large as England will need to be cleared for monocrop palm plantations. Some conservationists have warned that the biofuel programme is providing cover for the timber industry to pick off the remaining trees.

Attempts to switch to biofuel in Europe also pose a major threat to forests in Indonesia and Malaysia. Used cooking oil, or ‘yellow grease’, can be refined to produce biofuel, which is in high demand in European countries as a ‘sustainable’ energy source. The original idea – to run vehicles on chip-fryer fat destined for the bin – was a no-brainer, but European demand for yellow grease now vastly outstrips supply, so most of it has to be imported. Outside Europe, though, used cooking oil is mixed into livestock feed, among other things; its status as a waste product is geographically contingent. Exporting states are incentivised to use other forms of fat to supplement animal fodder so they can sell the used cooking oil that makes Europeans feel virtuous. This too leads to more oil palm plantations.

The horrors of fossil fuels are now so well known that we’re primed to accept lesser evils, especially if they’re rebranded in the language of virtue. But burning fresh biological matter is not so different from burning the same stuff once it’s been tamped down in the earth for a few million years. The point is to stop the burning.


  • 30 April 2021 at 9:56am
    Charles Evans says:
    Thanks for this great piece. I work with a colleague at my University whose research is into bioenergy. They found that, with certain combinations of biomass sources and combustion procedures, biomass could be significantly less carbon intensive than fossil fuels - however there were also scenarios where biomass combustion was more carbon intensive than fossil fuels!

    I can see the argument that our transition away from fossil fuel combustion, to entirely non-combustion sources of energy, will inevitably have to go through some intermediate stage. The entire world seems built on burning stuff for energy, and a sudden, total halt to all combustion seems too much a shock for society to handle. I'd hope that, if biomass is a section of the path to a zero-carbon future, it's a very short one!

  • 13 May 2021 at 8:01am
    Myotonic Jerk says:
    It seems unfair to comment on Indonesian palm plantations without mentioning the much less energy efficient European growers of rape seed and the like. Is it just that the Europeans got their deforestation in early enough to avoid criticisim?