Grain treatment uses gas to get rid of pest peril

11 January 2002

Energy crops show promise

RENEWABLE energy crops are a good prospect for the future, with Miscanthus showing distinct pro-mise. But farmers should beware of planting unless they are offered at least a 15-year supply contract.

That was the message from ADAS renewable energy project manager Mike Bullard at the Association of Applied Biologists biomass and energy crops conference in York.

"Overcoming planning rules for building new energy plants has been the biggest hurdle to progress so far. But this is being overcome gradually," he said.

"Until more plants are built, viable contracts and grants to grow energy crops are limited to farmers within a short distance of existing stations. That means only pioneer farmers living in the right place can take advantage of this sort of diversification. But there is hope that the industry will be able to scale-up."

Dr Bullards research into Miscanthus elephant grass has shown the crop can be produced economically over a wider area of England and Wales than was previously imagined. "Almost anywhere in lowland England is capable of producing economic returns, with dry matter yields of about 12t/ha possible in areas such as the Vale of York. That could be worth £20-40/t."

15-year contract

"But do not start growing the crop on a promise. Make sure you have a 15-year contract or at least that there is a plant which has actually been built close to the farm."

John Hewson, from Elean, the worlds largest straw-fired power station, told delegates that crops such as miscanthus could replace straw as the main energy source for producing electricity at the Cambridgeshire plant.

"Straw has to be stored and that costs money. We are looking at alternative crops that can be harvested all year round. Over the next two years, we will have 500ha of miscanthus being grown by farmers close to Elean and at a plant near Corby, Northants

"The crop is being grown on contract to take away the risk and will provide 10,000 tonnes of fuel. But this is only the beginning. Eventually, we hope to increase this amount so the plant can provide enough electricity to power an entire town."

The money being paid for Miscanthus uses straw prices as a benchmark. But dry matter yields are much higher at 16-20t/ha, Mr Hewson added. &#42

Grain treatment uses gas to get rid of pest peril

By Amanda Dunn

MODIFIED atmosphere treatment is simple to use, needs little labour, can be done with grain in-situ and costs about the same as conventional fumigation. It can also be used to halt fungal growth while damp grain awaits drying.

All it requires is commercial uptake, according to CSLs Chris Bell.

"The system burns propane to produce a low oxygen atmosphere which starves insects of oxygen." To disinfest a bulk, grain is sealed, the combustion gas introduced and the modified atmosphere held for four weeks.

"To seal the grain, place a plastic sheet over the surface and tuck it in at the edges of the bin or store," says Dr Bell. No extra sealing is required unless there is an auger entrance, which may need closing off.

"Gas is then introduced via a hose from the burner to the store ventilation system."

With grain at 20C, a level of 1% oxygen is maintained for four weeks. With cooler grain, when life cycles may be somewhat extended, eight weeks may be needed. Running costs for a 1000t store at 1% oxygen are about 40p/t/month.

Research on using the technique to protect grain throughout the storage season has also been carried out.

"If you start with clean grain, a less stringent atmosphere of 5% oxygen would provide sufficient protection, costing closer to 30p/t/month."

Localised treatment may also be investigated. "If you find a localised hot spot it may be possible to treat just that area rather than the whole bulk. A sheet could be placed on the surface, five or six probes inserted into the area and gas applied."

There is scope to integrate the technique with cooling and drying strategies, he believes.

"If you have insufficient capacity to dry grain quickly, lowering the atmosphere to 0.2% oxygen will prevent fungal growth. Growth will recommence if the atmosphere is lifted, but for grain waiting to be dried and in danger of losing condition, modified atmosphere may prove of benefit."

Chemical fumigant

The main drivers for the research were the phasing out of methyl bromide as a chemical fumigant and doubts over the use of phosphine, says Dr Bell.

"While it may take several years before this technology is taken up by industry, we have a technique that works and the ability to keep grain pest-free without reliance on chemicals." &#42

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