Bioenergy - draft policy statement: consultation

Annex C – Overview of Bioenergy with Carbon Capture and Storage (BECCS) technologies

BECCS Power and CHP

Retrofitting post-combustion carbon capture technology on plants which are currently utilising biomass feedstock would help in reducing emissions while still being able to benefit from utilisation of the available biomass resources.

BECCS power plants can be used to deliver baseload, or continuous power output. This would deliver the greatest emission reductions particularly where heat is recovered and used on or offsite, for example, in heat networks.

BECCS plants could also provide an alternative source of dispatchable power, which provides resilience and flexibility to our electricity system to complement other renewable generation technologies. At present, dispatchable power is provided by unabated fossil fuel power stations. BECCS power would have access to an alternative income from flexibility markets while removing carbon from the atmosphere.

Industrial sites which have ready access to bioresources could operate BECCS (CHP) whilst meeting emission reduction targets and benefiting from the UK ETS. Scotland currently has three medium sized biomass power plants which, if retrofitted with CCS, could represent a significant BECCS contribution. Research on NETs technologies estimated that over 95% of their emissions are biogenic, which could result in significant yearly negative emissions.

BECCS Energy from Waste

BECCS energy from waste (EfW) operates in a similar way to BECCS power plants, producing either power and/or heat, but using waste (usually household and commercial) as a feedstock rather than only biomass. Also, like the BECCS power generation process, waste may be initially combusted with subsequent capture of CO2, or gasified.

Managing waste using EfW produces emissions in the form of CO2, however, depending on the composition of waste, these are generally lower than landfill, which produces methane through degradation of biodegradable waste. A Zero Waste Scotland report found that, on average, sending one tonne of municipal waste to EfW in Scotland in 2018 emitted 246 kg CO2e/t, which is 27% less than sending it to landfill, although this is dependent on waste composition, which can vary and is likely to change over time.

Waste should be treated according to the waste hierarchy, which prioritises waste prevention, reuse and then recycling over energy recover, through EfW for example, and disposal. Circular economy and waste policies aim to treat materials as far up the waste hierarchy as possible, resulting in a continued reduction and minimisation of waste sent for energy recovery or disposal.

BECCS Biomethane

Capturing CO2 from upgrading biogas to biomethane is a well-established technology. Advance combustion technologies such as gasification or pyrolysis can also be used and allow carbon capture when the resulting syngas is upgraded to biomethane. Both techniques can utilise a range of residues, by-products and waste as feedstock.

BECCS distilleries and breweries (Fermentation)

The fermentation process at breweries and distilleries produces CO2 which could easily be captured. Bioethanol production also features a fermentation stage and would allow carbon capture. These processes require sugary or starchy feedstock.

BECCS Hydrogen

Biohydrogen can be produced by removing carbon from biomethane or from gasification of biomass, where biomass is heated without combustion to produce syngas. The syngas can be used to produce heat and power or upgraded to hydrogen.

Biochar

When biomass is heated in the absence of oxygen, such as when processed via pyrolysis or gasification, it can produce biochar. This charcoal like substance can be applied to soil as a means of storing the carbon and improving soil quality. There are a number of other potential uses for biochar which may develop, such as wastewater treatment, flood mitigation, green cement and to improve energy output from AD plants. Further research is required to establish the permanence of storage and optimum use for the product.