Could the use of agricultural residues, such as straw, help to reduce the need for fossil fuels and add value to existing food crops?

Researchers at Harper Adams University College, Shropshire, are currently investigating the viability of using oilseed rape straw (OSR) pellets as an alternative to traditional fuels.

It has long been known that although fossil fuels are the main source of energy, they also contribute greatly to global carbon dioxide emissions. Renewable energies, such as wind, solar, hydro and tidal have since become the desired alternative.

As part of its commitment to EU targets, the UK needs 30% of all renewable electricity and heat to be obtained from biomass, material derived from living, or recently living organisms, by 2010.

Leticia Chico-Santamarta is a postgraduate researcher at Harper Adams, she said: “There are two main sources of biomass for energy generation; purpose grown energy crops and residual materials from food crops. Using agricultural resides avoids the food vs. fuel dilemma and may add value to existing food crops.

“At the moment, there isn’t a significant market for OSR straw in the UK, and a lot of it is chopped into the soil through ploughing. Developing a market would add value to the gross margin of the crop at farm level.”

The research, which is funded by Claas Stiftung and the Douglas Bomford Trust, includes investigating the pelletisation of the straw, the effect that storage has on their value and quality, and the combustion behaviour of OSR straw pellets.

Leticia added: “By making the straw into pellets and increasing the bulk density, the net energy content per unit volume is also increased. Storage, transport and handing of the material are easier and cheaper, with pellets having a 42% weight advantage over straw.

“To investigate the quality during storage, we have been conducting different tests, such as durability and compression tests, to see what effect handling and storage has on the material.”

The final stage in the investigation is a combustion test at the Energy Technology Centre at Cranfield University. For each combustion test, the emissions, temperature and amount of ashes are recorded.

Converting the straw into pellets has other benefits. Because generally it doesn’t need to be dried, the energy required to do so is low compared with other materials- approximately 5% of the energy available in the straw.

To complete this project, Leticia and the researchers at Harper Adams hope to study the mechanics of forming OSR pellets and the behaviour of the straw under compression.

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