Chapter 2: Biomass

Introduction

Biomass is the burning of wood or crops for energy. Mankind has relied on it since first burning firewood. With industrialisation in the 19th and 20th centuries, it got displaced by more abundant and energy dense fossil fuels like coal (and later oil and gas). In Britain today, the mostly used biomass is in wood fires stoves heating homes and at the massive Drax power station.

What's good about biomass?

Before slating it, it's worth noting biomass technologies have a number of advantages:

• Flexible storage: biomass fuels such as wood pellets, biodiesel/ethanol can be stored in silos or big tanks just like fossil fuels, ready to be burnt when they're needed. Compared to electrified renewable technologies like wind and solar, they don't necessitate storing energy in batteries that use rare earth materials, and they're often not too much of a risk to the environment when they're stored. They can also be used for heat (e.g. a stove), transport (e.g. a biodiesel car/truck) or power generation (e.g. Drax).
• Conversion: you can often repurpose or convert existing fossil fuel appliances to run on biomass fuels. Drax power station previously burnt coal, diesel cars and trucks can be converted to run on vegetable oil derived biodiesel, coal fireplaces can be retrofitted with a wooden stove.
• Consumer Adoption: because they're tangible and similar to fossil fuels, they're often easier to persuade consumers to switch to. Biodiesel and bioethanol fuelled cars engender less range anxiety than EVs. Biomass boilers require less modification to home radiators than heat pumps.

So what's the problem with Biomass?

In a nutshell, biomass isn't efficient. It's a very old technology, dating to cave people's first use of firewood, and we have to rely on some plant's growth cycle to capture stored energy. Plants aren't that efficient at storing the energy they photosynthesize from sunlight. To get any meaningful contribution to our energy needs from biomass requires large scale cultivation of crops and plants. And when we burn biomass fuels in power stations or stoves, we are lucky to usefully extract 30 or 40% of the energy the plants have captured. All together, this means to get any significant proportion of our energy from biomass requires converting massive tracts of land to growing large numbers of similar plants or crops. Such monocultures can't fail to have profound impacts on ecosystems affecting other wildlife, and competing with use of land for food production.

How do you solve a problem like Drax?

Drax is massive. It is the largest power station the UK has ever had, with a capacity of 3,960 megawatts - enough to power over 6 million homes. It was built in 1974 in Yorkshire on the banks of the River Ouse, to burn coal sourced from the nearby Yorkshire coal fields. At the time, almost all Britain's power came from coal, and there were many other power stations like Drax. In the rivers like the Ouse, Trent, and Aire that empty into the River Humber, the area was nicknamed "megawatt valley" and accounted for over 40% of Britain's power generation at its peak. When Drax opened in 1974, it was the largest coal-fired power station in Europe and one of the biggest in the world - a symbol of Britain's industrial might and energy ambitions. At its peak, Drax was one of the largest carbon emitters in Europe, releasing over 20 million tonnes of CO2 annually - more than many entire countries. While there are larger coal plants in Germany and Eastern Europe, Drax was certainly among the biggest emitters in Western Europe.

When the UK signed up to the EU Renewable Energy Directive in 2009, it committed to generate 15% of its energy from renewable sources by 2020. At the time, only around 3% of Britain's power was from renewables, and the challenge seemed daunting, especially as Britain's most established low carbon generation technology, nuclear power, couldn't be used toward the target. Now as it turned out, in 2020 Britain generated 24% of its power from wind and a further 4% from solar, because these technologies fell drastically in price and were deployed at scale around the country in a way that exceeded earlier expectations. So Britain never needed Drax to meet this target. Britain also left the EU in 2020-1, which certainly wasn't expected in 2009!

Successive governments and energy ministers have been terrified of losing Drax's generation capacity. In particular, the spectre of 1970s blackouts haunted Conservative administrations from 2010-2024, creating a political climate where keeping the lights on trumped all else. So when Drax's owners proposed converting initially two generating units in 2012, and then two more in 2016 and 2018, ministers decided to bend the rules for subsidising renewable technologies to include biomass. This wasn't entirely unprecedented—dedicated biomass power plants had been receiving Renewables Obligation Certificates since 2002, typically earning 1.5 ROCs per megawatt-hour of electricity generated. Examples included Steven's Croft Power Station in Scotland (44 MW, operational from 2008), which burns a mix of 60% waste from timber production, 20% coppiced wood, and 20% recycled fibre, and the Elean Power Station in Cambridgeshire (38 MW, operational from 2000), which burns straw, oilseed rape, and miscanthus. At current ROC values of £64.73 per certificate, 1.5 ROCs provide an additional £97 per MWh on top of the wholesale electricity price.

The first two Drax units (2012) received Renewables Obligation Certificates (ROCs), while the later units (2016-2018) received Contracts for Difference (CfDs) through a separate non-competitive arrangement called a "Final Investment Decision" (FiD) enabling contract, which unlike the transparent auctions for wind and solar wasn't a very open or competitive process. Instead, it was more of a direct negotiation between Drax's private owners and government ministers and civil servants. The guaranteed prices Drax gets for its power are around £150-170/MWh today, and are guaranteed to increase each year in-line with inflation for 15 years after the conversion process, meaning between 2027 and 2033.

Given the quantity of wood pellets Drax needs to meet its annual energy requirement of around 20,000 GWh, it couldn't rely on British (or even European) sourced wood. So it turned to North America. The environmental and social impacts of this large-scale wood pellet industry have been extensively documented, including in a BBC documentary.

Despite the concerns with Biomass, the price paid for Drax's power is significantly more than other power generators:

Conventional power plants receive only the wholesale electricity price, currently around £50-80 per MWh depending on market conditions. New wind projects those under consideration today (for the upcoming AR6 subsidy round) are expected to get £110-150/MWh in today's prices.

Wood stoves and pellet boilers - smoke and subsidies

As well as being used in the largest power station in the country, biomass is well established for heating homes and buildings. Wood fires are aesthetically pleasing, and stoves and biomass boilers can achieve 70-85% efficiency, comparing favourably with gas and oil boilers which typically achieve 85-95% efficiency. In many rural areas, routine tree surgery creates a ready supply of timber, making biomass an attractive local energy source. Wood stoves are resilient to blackouts too.

However, the growth of wood burning in urban areas, particularly during the 2022 energy crisis, has created significant air pollution problems. Wood stoves and open fires emit high levels of particulate matter (PM2.5 and PM10), nitrogen oxides, and other harmful pollutants that contribute to poor air quality and respiratory health issues. These are localised pollution problems, in contrast to the global nature of climate change. In response, the government has introduced regulations to phase out the sale of the most polluting fuels and stoves, with new restrictions on wet wood and coal sales coming into effect in recent years.

In Northern Ireland, subsidies for Biomass became particularly controversial when the Northern Ireland Audit Office revealed in 2016 that a subsidy to promote biomass use in smaller businesses (like farms) had been overly generous. Because the subsidy offered exceeded the cost of wood pellets, businesses had an incentive to burn as much biomass as possible. This experience has rightly made subsequent governments around the UK more critical

Biofuels

Less topical of late, petrol and diesel are required to contain 5-10% of biofuel, typically derived from crops like corn, sugarcane, and palm oil. This creates a direct competition between fuel and food production, as agricultural land is converted from growing food to growing energy crops. The result is often large-scale monoculture plantations that replace diverse ecosystems, reduce biodiversity, and can drive up food prices in regions where these crops are grown. In some cases, the environmental impact of clearing forests for biofuel plantations has been so severe that the carbon emissions from land-use change exceed the carbon savings from using biofuels instead of fossil fuels. The cost of manufacturing biofuels significantly higher than fossil fuel derived petrol and diesel too, at least before taxes are added.

Perhaps worth mentioning some quantification of the inefficiency of said biofuels. Suppose oilseed rape is used as an input to the production of biofuel. Rapeseed yield can be up to 3,000kg/ha per harvest, i.e. 0.3kg/m²; 1kg rapeseed contains about 0.5kg oil; with oil containing 38MJ/kg the energy gained is consequently 5.7MJ/m². This energy spread over one year (1 harvest per year) results in 5,700,000J /365/24/60/60 s = 0.180W/m² average power. Conversion to bio-diesel incurs certainly some additional losses. In contrast, the solar irradiation at sea level is about 1kW. With on average 4h/day and an efficiency of 20%, a 1m² solar panel would produce an about 10004/240.20 = 33W average power. Therefore, a factor of 184 more power can be harvested from solar panels than from growing rapeseed to produce biofuels. Consequently, biofuels from crops are indeed questionable in terms of efficiency.