Growing Energy

Bio-fuels are fuels derived from biomass - that is plant material, vegetation, or agricultural waste. Like coal and petroleum, biomass is a form of stored solar energy, the energy being captured through the process of photosynthesis. As well as providing a sustainable energy source, bio-fuels can also be carbon neutral - releasing into the environment only the carbon dioxide that they have taken from the environment during their growth.

So what is the potential for bio-fuels? In April, the House of Commons Environment, Food and Rural Affairs (EFRA) Select Committee set out to discover this. The RSC and the Bioscience Federation were invited to give oral evidence to the inquiry. 

Bio-fuels

In the UK the current options for bio-fuels are bio-ethanol from the fermentation of sugars in sugar beet or cereal crops and bio-diesel from oilseed rape. In its July report The Energy Challenge1 the Department of Trade and Industry discusses increasing the Renewable Transport Fuel Obligation (RTFO) to 10 percent by 2015. Currently bio-fuels account for a little under 2 percent of transport fuels used in the UK.

Taking into account exported wheat and set-aside farm land, the UK could produce a maximum of 5 percent of its current road transport fuel requirement. To satisfy the RTFO without significant bio-fuel imports will need technological advances.

The RSC highlighted to the Select Committee several new technologies that could be used to produce bio-fuels. Lignocelluloisic materials, such as wheat straw, could become economic to process into fermentable sugars. Such bio-ethanol production from agricultural and forestry waste would alleviate the need for dedicated crops.

Thermal conversion processes also have the potential to produce bio-fuels. For example, rapid heating in an oxygen free or restricted environment converts biomass into synthesis gas (carbon monoxide and hydrogen) that can be upgraded into liquid fuels via a catalysed reaction (the Fischer-Tropsch process).

Biomass for power generation

In addition to transport fuels, biomass, fired in dedicated plants, or co-fired in coal burning plants, has a potential for combined heat and power generation (where heat produced during electricity generation is recycled for domestic or industrial use). Sweden is a globally acknowledged world leader in using biomass for power generation. 25 percent of Sweden's energy needs are satisfied with bio-energy. 

In the medium term, around 5 percent of UK electricity could be generated from biomass. A number of UK coal-fired power stations are currently co-firing imported biomass (such as imported olive waste and milled palm nuts from Malaysia).  

Maximising output: the bio-refinery

A bio-refinery integrates biomass conversion processes and equipment to produce fuels, power, and value-added chemicals from biomass. The concept is analogous to today's petroleum refinery. By producing multiple products, a bio-refinery maximises the value derived from the biomass feedstock. A bio-fuel may be its major product, with a series of higher value co-products (for example pharmaceutical intermediates) as well as electricity and heat. 

Marine biomass

The RSC also pointed out the potential of the marine environment as a source of biomass. Research by the Scottish Association for Marine Science (SAMS)2 has demonstrated that macro-algae are cultivated easily, grow prolifically (increasing biomass by up to 10 percent per day) and sequester carbon. 

Additionally, anaerobic fermentation of seaweed can yield methane at a higher yield than any other source of biomass.  SAMS has developed methods for producing large volumes of seaweed inshore and is currently investigating the economics and feasibility of the process, from culture to methane production.

Is it really carbon neutral?

Energy is consumed in producing bio-fuels, from the agrochemicals used to grow biomass and the heat used to convert it to bio-fuels, to the fuel used in transportation. This all impacts upon carbon reduction adversely (unless renewable energy is used).

Carbon emissions can be minimised throughout the life-cycle of bio-energy production by the application of good science and engineering, agricultural best practice, maximising the use of biomass co-products (either for chemical or energy production) and by minimising transportation. Any move to import bio-fuels to make up the UK shortfall needs to be seen in this context and may be counter-productive.

Impact on biodiversity

Any change in agricultural practice will undoubtedly have an impact upon biodiversity and the social use of land. It is important that we understand the implications of such changes.

Utilising agricultural and forestry waste would have limited impact, but the impact of large-scale farming for bio-fuels will depend on what is grown.

Evidence exists that short rotation coppice, an energy crop consisting of high-yielding willow or poplar, has very positive impacts on flora and fauna. In a 3-year cutting cycle, canopies of differing heights form, encouraging different ecosystems.

Learning from examples

The UK can learn from and collaborate with countries where expertise and supply chains have already been developed. In Brazil, 60% of all new cars can run on a fuel mix made up of 85% bio-ethanol. Germany already has the capacity to produce over 2.5 million tonnes of bio-diesel and as discussed, Sweden is the world-leader in biomass combustion. These examples will provide invaluable knowledge that must be appropriately tailored to UK conditions.

The potential for bio-energy

Bio-energy could play a significant role in the provision of heat, power and road fuels in the UK, but we must be realistic about the contribution that biomass can make in filling our energy gap.

Currently, direct combustion of biomass for heat and power generation appears to offer more significant benefits, in terms of carbon emission reductions. Technological advances will continue to improve the contribution bio-fuels can make.

Policy and regulation

Legislation and policy tools offer an opportunity to encourage best practice in biomass and bio-fuel production and should be used to encourage practices that minimise energy requirements, cost and environmental impact.

The Government has committed itself to extending policies such as the RTFO and the renewable obligation (RO), which requires power companies to generate a portion of their electricity from renewables. 

These policies will be crucial in encouraging investment - the Government must continue with a long-term framework of regulation and incentives that will give industry the confidence to make a financial commitment. If this is not achieved, there is a risk that the UK will become reliant upon imported sources of bio-energy to meet government targets.

The Select Committee is due to release its final report in September. The RSC has stressed the importance of chemistry, bioscience and engineering in delivering future bio-energy technologies and the need for a UK bio-energy roadmap to focus research and development efforts.