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Bioenergy: new blooms, but also prunings

By Dave Elliott

In an opinion survey by YouGov for the Energy Technologies Institute, 80% of respondents supported an increase in bioenergy use in the UK. Around 74% supported producing bioenergy from biomass and 81% backed producing biomass from waste, comparable to levels of support seen for other renewables. However, some environmental groups strongly oppose some types of biomass use and there is a sometimes rather heated debate underway, as this extended post explores.

The first area of contention is land use. The ETI noted that over a third of respondents were concerned about biomass competing with other land-uses such as food production, though the ETI says case studies show they can complement each other – the institute has also recently published a report on that, which says that it can help UK farmers diversify their income and increase the productivity of their land. The ETI says that initial investment costs can be paid back within 6-7 years and the impact on food production can be minimised or avoided by optimising the use of land.

That’s all basically about biocrops. What about forestry wastes and, especially, imported wood pellets? The opinion survey says the results suggest that the public would be ‘comfortable with a mix of imported and domestic biomass feedstocks’, provided imports are used in addition to, not instead of, domestic sources.

That is unlikely to be welcomed by groups like Biofuelwatch, who strongly oppose the use and import of US wood pellets. The group has been amongst those challenging the Drax bioconversion project, aided by a US NRDC assessment of the environmental viability of US wood pellet production. The UK’s Renewable Energy Association came back with a riposte.

However, Biofuelwatch, along with NRDC and Friends of the Earth, wants the government to remove biomass conversion from the list of CfD-eligible technologies since they say it’s not low carbon and the use of forest biomass depletes carbon sinks. That got some backing from a new report from Chatham House that says: ‘Overall, while some instances of biomass energy use may result in lower life-cycle emissions than fossil fuels, in most circumstances, comparing technologies of similar ages, the use of woody biomass for energy will release higher levels of emissions than coal and considerably higher levels than gas.’

The Renewable Energy Association came back with the comment that ‘This report hangs on the fallacy that it takes decades for a forest to recapture carbon. That isn’t true. A well-managed forest is continually growing and it locks in carbon at an optimal rate.’

But the Chatham House report seems to accept the view, by opponents to the use of forest-derived wood pellets, that they are not just sourced from incidental fellings/offcuts, but from whole tree round wood. What’s more, it says If slow-decaying residues are burnt, the impact would be an increase in net carbon emissions potentially for decades. In addition, removing residues from the forest can adversely affect soil carbon and nutrient levels as well as tree growth rates’. And it says that in any case ‘Forest residues are often unsuitable for use because of their high ash, dirt and alkali salt content’.

The message certainly got across, with the debate continuing. The REA issued what might be seen as a definitive riposte, and this link offered a helpful overview. The IEA chimed in with this.

While the debate over forestry wood continues, Biofuelwatch has also come out strongly against what might be seen as a somewhat less worrying idea. Ecotricity has recently been granted planning consent for the UK’s first biomethane plant using grass as the main feedstock. The company sees it as far better than fracking.

Although Ecotricity is not proposing this idea at present, Biofuelwatch focuses on its claim that such “green gas from grass” could in theory replace 97% of natural gas for domestic heating and hot water by 2035, whilst helping restore biodiverse, flowering grasslands. Biofuelwatch doesn’t think this will be at all ecologically viable. It says that ‘replacing current domestic natural gas use with biomethane made from grass would require an area of 10.2 million hectares, which is 59% of the UK’s entire agricultural land. This area is equivalent to 92% of existing grassland in the UK, most of which is used for grazing. Such a large-scale grass-to-biomethane programme would therefore all but end livestock grazing and make the UK almost entirely dependent either on meat or dairy imports, or on animal feed imports for domestic factory farming. The greenhouse gas emissions from indirect land-use change will be very considerable, and could be far greater than the CO2 emissions saved by burning less natural gas’.

Well yes, in this very extreme example – although maybe a reduction in meat eating and production would be no bad thing. However, Biofuelwatch goes further: ‘This is not the only climate-related concern: firstly, upgrading biogas to biomethane requires the CO2 contained in the biogas – up to 45% of the total volume – to be emitted straight into the atmosphere, without burning. Secondly, and more worryingly, both biogas digestion and upgrading to biomethane are associated with methane leaks. Depending on the scale of those leaks, biomethane could have a seriously adverse climate impact. Little data exists about actual methane leakage rates from such plants.’  

Well, these are issues for any type of biogas production. Biofuelwatch seems to oppose them all, although it is evidently especially concerned about grass: ‘Biogas and biomethane plants using grass, i.e. a non-waste feedstock, do require an environmental permit and there is no requirement to reduce or prevent methane leakage, nor to monitor it.’

Finally, the organisation looks at Ecotricity’s biodiversity claims. Biofuelwatch says ‘grasslands could in theory be managed for wildlife while supplying a biogas/biomethane plant. Maximising yields, however, will require sowing ‘optimised’ rather than diverse grass mixtures, using herbicides and fertilisers, and cutting grass more often and at different times than is beneficial for wildlife. Those claims by Ecotricity thus cannot be substantiated either’.

To some extent, Biofuelwatch seems to be attacking a straw man (or rather a grass man). Ecotricity has accepted that major programmes would be hard and would use large amounts of land. Even their proposed 10 MW AD “gas mills” would each use 5,000 acres to produce enough energy for 5,000 homes – 1 acre each. Scaling up to 500 of them would obviously have more significant land use, 2.5 million acres, but that could, they say, meet the expected 2020 green heat shortfall, 42.5 TWh pa based on the UK target of getting 12% of heat from renewables; so far we had 4.9%. However, that’s about as far as they seem to go at present: the 97% concept is far off, and with Biofuelwatch on the case, it may stay that way!

Ecotricity does say there would be no need for fertilisers and they would stick to non- arable marginal land. Mind you, solar farms are after that as well! And clearly the land-use issue will not go away. So this debate will continue.

Biofuelwatch does support most (other) renewables, including those that use land like wind and solar, but Biofuelwatch evidently sees almost all bioenergy as a bad idea. That even extends to BECCS – Biomass Energy with Carbon Capture and Storage, which some see as offering a carbon negative energy option. By contrast, as noted in my last post, the Energy Technologies Institute sees this as very promising. That debate will continue too – with the Chatham House report also challenging BECCS…

On the ground though, and less controversially, some forms of bioenergy are making practical progress, those involving farm and domestic food wastes especially. The 2015-2016: When Gas Turned Green report by the Anaerobic Digestion and Bioresources Association (ADBA) says that, in the UK, the total number of operational anaerobic digestion (AD) plants has increased from 424 a year ago, to 540 today. AD now has a capacity of over 708 MWe, equivalent to the capacity required to power 850,000 homes – a rise of 35% from the same time last year. And biomethane injection into the gas grid supplies heat to around 170,000 homes.

Some AD biogas might be used for vehicle fuels (for tractors, for example, or trucks), but the production of liquid biofuels for vehicles is a separate, significantly controversial, issue. However, given that land-use is a key part of that, some say why not look at arid zone biomass like cactus. That could be a major new biofuel option, as well as a source of biomass for other end uses, with low eco-impacts and low water use. Here are two early reviews – one suggesting that 10,000 TWh of heat p.a. might be available globally.

There are of course also other options for transport – something I will be looking at in my next post.

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