For more than a decade the ETI has invested in the assessment of the potential for different UK bioenergy value chains. We have undertaken research and developed technology to demonstrate the importance of bioenergy to a decarbonisation agenda and hopefully helped to fill knowledge gaps within the sector. However, as demonstrated by the ETI’s whole energy system analysis, if we fail to develop the role of bioenergy beyond today’s level it will potentially cost the country an additional £200bn to meet its carbon targets.
Bioenergy is one of the largest and most versatile sources of renewable energy in the UK, with the potential to provide around 10 per cent of the country’s energy needs by 2050. Combined with carbon capture and storage, the decarbonising strength of bioenergy becomes even more effective, delivering net negative emissions (which is needed to meet UK climate targets) of approximately -40Mt CO2 per year in the 2050s. This is just under half the UK’s emissions target in 2050 and reduces the need for other, more expensive, decarbonisation interventions across the wider energy system.
In order to meet these bioenergy targets, the UK will need three times more energy feedstock than is currently used today and efforts to increase the area of energy crops will need to focus on overcoming both market and technical barriers. Blending second generation crops and finding alternative end uses could help to overcome the ‘chicken and egg’ factor that can hinder investment decisions. Farmers want a reliable market to sell into before taking the decision to plant and potential end users don’t want to invest in setting up dedicated energy crops supply chains too far in advance of operations. Developing new markets is one way to promote the acceleration of planting rates for energy crops across the UK.
It is important to note that the characteristics of these emerging feedstocks are different to commonly used wood chips and pellets, and if not managed properly, this could cause problems in boilers and other conversion technologies. To successfully integrate new feedstocks, either the end user must be able to accept greater physical and chemical feedstock variability, or feedstock production techniques and pre-processing must be used to standardise feedstocks qualities.
This increase in the use of biomass feedstocks will bring with it, because of the different types of biomass crops available to the UK, more variability in feedstock properties which end users will need to be able to accommodate. One solution to avoid added costs is to pre-treat biomass feedstocks which will reduce the impacts of variability on end users. But pre-treatment in itself adds costs in the supply chain.
The Techno-Economic Assessment of Biomass Pre-Processing project was commissioned by the ETI to understand the impact these pre-processing technologies could have on UK bioenergy chains. Led by project partners E4tech, it set out to assess when it pays to pre-process biomass. We wanted to understand the circumstances under which pre-processing can reduce costs, lower emissions and increase efficiency to inform industry on the most effective technology and encourage commercialisation.
A range of pre-processing technologies was studied, including forced drying, steam explosion, torrefaction, pyrolysis, water washing and chemical washing. The project found that water washing was the most effective at improving biomass characteristics. Water washing is a low cost, low energy process which is used to remove biomass surface contamination and encourage the leeching of problematic species associated with slagging, fouling and corrosion in boilers. We found that this would provide a more economic pre-processing step for extremely contaminated feedstocks.
When looking at the economic and performance relationships for each pre-processing technology, it was found that water washing provides the most effective potential trade-off between the downstream benefits of improved biomass quality and the added costs of washing and then drying the biomass.
So where are we now? The University of Leeds has demonstrated, at lab-scale, the potential for water washing to reduce levels of contaminants in waste wood feedstocks and reduce variability between samples, but we are yet to see the technology deployed at a commercial scale for energy crops. Currently, commercial scale water washing machinery is used in the agricultural industry to wash potatoes and sugar beet. We believe if this can be successfully adapted for biomass, water washing could be deployed relatively rapidly, helping to keep the UK on a trajectory to scale-up its domestic biomass production and contribute to a transition to a low-carbon UK energy system of the future.