The crucial UN climate change talks taking place in Copenhagen this December have put climate change back in the spotlight, but while world leaders prepare to discuss the best way to reduce global CO2 output, the power and food industries have already teamed up to demonstrate their commitment to producing an environmentally friendly processes.
As part of Wartsila's portfolio of clean energy projects, the Finnish power giant has built two biomass-operated CHP plants in England, one in Newcastle and the other in Tadcaster, for brewer Scottish & Newcastle (S&N). We spoke with the company's biomass business leaders about the technology and the plants' use of spent grain, a by-product of the brewing process.
Ozge Ibrahim: How do the two CHP biomass plants work?
Wartsila: The biopower 5 plants produce steam and electricity for the breweries' processes, and export electricity to the local electricity network. Each plant has an electrical output of 3.1MWe and a thermal output of 7.4MWth. The electrical output in condensed mode operation is 4.7MWe.
OI: What biodegradable materials are used to operate the plants?
W: The plants burn a mixture of spent grain from the brewery and wood chips from local sources. Spent grain is a by-product of the brewing process, the grain remaining after the fermentable sugars have been extracted during the mashing process. It consists of solid residue.
The spent grain is delivered from the brew house with a moisture content of approximately 80%. It is then passed through a belt press, which reduces the moisture to 58-60%, a level suitable for the BioGrate [Wartsila's patented combustion technology, made up of a rotating design with a conical primary combustion chamber in which fuel is fed to the centre of the grate from below].
OI: How do you ensure the high content of nitrogen and sulphur in spent grain does not cause elevated levels of chemical output? Is the technology you use to adjust levels of CO2 and other gases working as originally planned?
W: Biomass materials typically contain equal proportions of the energy-producing elements carbon (C) and hydrogen (H). The level of sulphur (S) in dry material is low but can sometimes increase because of additives from the industrial processes.
The content of nitrogen (N), which can cause the formation of acidic compounds in the flue gas, can typically vary between 0.01% and 1%. The level of chlorine (Cl), which produces corrosive flue gas compounds, is also low in clean fuels.
We have run guarantee tests to ensure balanced operation of the plants.
OI: What is the key driver behind your decisions to use certain technology?
W: The need to reduce CO2 is the main driver – we develop our plants constantly towards CO2-free production. The key drivers for our businesses are the EU's 2020 targets for sustainable energy production.
OI: The two power plants for S&N are seen as a major step towards sustainable energy self-sufficiency for the brewing industry. Do you have other similar projects in the pipeline?
W: These are the first spent grain-related projects for us in the UK. We are also, for example, interested in the by-products of the ethanol industry.
OI: Are rising commodity prices and the current economic climate affecting the running of these and other biomass-fuelled plants?
It seems that CO2-related costs raise the price of fossil fuels. Biomass becomes more attractive when this happens, and the price of biomass then goes up.
The availability of biomass and price-related issues make opportunity fuels and industrial residues such as spent grain more interesting.
OI: Are there any new ideas to enhance production and efficiency at the plants in England?
W: Overall we are interested in the constant development of efficiency, such as CHP plants utilising heat loads efficiently.