Biofuels : IN DEPTH: The Role of Biomass within Energy Supply

The shift towards sourcing cleaner, renewable forms of energy means that there has been a subsequent increase in the combusting of organic matter, otherwise known as biomass, often sourced from wastes, as a fuel. So as the energy mix changes, what will be the long-term role of these fuels?

Around the world, many power stations have switched to the use of compressed wood pellets as a renewable energy source, which in turn helps to reduce the level of carbon dioxide emissions. For example, in the UK this has been reflected by the fact that 37% of electricity in 2019 was generated via renewable sources, compared to 35% by fossil fuels.

Many automatically think of wood pellets when they hear the phrase ‘biomass’, but in reality it can mean absolutely anything that is of plant or animal-based origin. Rather than taking the form of something that is manufactured – such as a wood pellet – it is often a material that might be considered as a waste or a by-product. This includes coconut, pistachio, walnut shells, olive cake, bagasse (sugar cane residue), oat husk (residue after the removal of the oat kernel) or waste-derived fuels such as solid recovered fuel (SRF) and refuse derived fuel (RDF).

Biomass is also present in many types of fuel in varying concentrations. While it is most concentrated in biofuels, it is also a component of SRF and other waste-derived fuels. Power generation subsidies are calculated on the basis of the biomass energy content within the fuel, as this is regarded as a renewable energy source.

The terminology is often confused, but biomass is simply a component of biofuel. As biofuel is the term used within the international industry standards, it is the one that is more frequently used by professionals.

As the single largest worldwide source of biomass feedstock, biofuel pellets can be used within a wide range of applications. The feedstocks from which they derive can vary from hard and softwood sources to agricultural ‘waste’ products such as oat, sunflower and peanut husk, olive cake and straw.

Interestingly, there are no standards to determine the level of biomass content in biofuel, and it is generally accepted that biofuel in its strictest form is 100% biomass. There is, however, a standard for the determination of biomass content within solid recovered fuel, which includes analysis techniques such as selective dissolution (a wet chemistry method) and manual sorting.

The former is the most widely used throughout the industry given its relative accuracy and financial viability. However, the Office of Gas and Electricity Markets (OFGEM) promotes the use of a manual sorting method on its website as an alternative means for the determination of biomass content.

The standards are produced by technical committees working on behalf of the International Organization for Standardization (ISO). SOCOTEC is represented on these committees and actively participates in these discussions, with our Energy Services team in an ideal position to be able to contribute to this process and the resultant published standards thanks to our industry experience, expertise and heritage.

Determining the best biofuel is subjective depending on its application. Each one will have an associated fuel specification detailing its acceptable/ideal properties, which would be determined via the analysis of a representative sample. Analysis is also critical to understanding and monitoring whether there is anything in the fuel that could be damaging equipment or negatively affecting the outputs, such as ash and emissions which could be causing unnecessary environmental pollution.

Various technologies are used to convert biofuel into heat and/or power; for example, through direct combustion or gasification. When an application uses gasification technology, the process produces syngas, which is an abbreviation for synthesis gas. A number of benefits are seen to be obtained from the combustion of syngas rather than the biofuel itself, including the fact that it releases fewer particulates into the atmosphere.