Letter from Europe: Clean power from a new generation of fuel ideas

Sunday, January 4, 2009

Crops that produce their own electricity, intelligent greenhouses and sun-powered cattle-feeding robots – these are just some of the new strategies emerging for natural energy production

by NORMAN DUNN

The fuel-from-the-fields revolution hasn't lingered long with simple biogas, ethanol and biodiesel. Even second generation biofuels such as BtL (biomass to liquid), where biogas is liquefied to give highly efficient synthetic fuel, is now being overtaken by simpler, more efficient and even more climate-friendly strategies.

For instance: direct production of automotive fuel from crop cellulose – straw, corn stalks, wood trimmings – without any fermentation. Cooking these byproducts in a chemical soup is already producing new, high-energy liquid fuels. These have the tongue-twister names ethoxymethylfurfural (EMF) or 5-methylfurfural (MF).

Because there's no fermentation and gas-to-liquid conversion, these fuels from the field are much cheaper and simpler to produce. There's still a way to go yet in development, although EMF is being tested successfully in diesel blends now. But how much cheaper might such natural power sources be if we could do away with harvesting biomass altogether?

This is what scientists in the Netherlands' largest agricultural university at Wageningen are looking at just now. Photosynthesis expert Dr. Jan Snel and his team have found a way of collecting electricity from growing plants. Trials so far indicate that wiring up a particular kind of reed grass (Phragmites australis) has a potential production of 14 kW per hectare and hour. That's enough to supply steady power for around 28 households, say the Dutch researchers. Dr. Snel and his fellow scientists have developed what is now called a plant-microbial fuel cell (PMFC) to collect electrons naturally produced by bacteria working around the root systems of plants.

A graphite sphere is the main part of the PMFC. This rests against the root system and acts as an anode.

When bacteria electrons move from this anode to a cathode in the fuel cell, electricity is produced. Of course, there's still the painstaking practical work of finding how best to connect up the roots of growing crops out in the field. But just think of row crops like soybeans or potatoes. Surely it wouldn't be impossible to lay a cable with attached fuel cells while drilling or planting?

Whatever the practical problems ahead, the Dutch researchers are already planning to look into the power production capacities of commercial crops such as rice and tomatoes. Because tomatoes are often grown under glass using hydro culture in the Netherlands, this looks like the best bet for a quick commercial start into this method. After all, the roots in their water/plant nutrient bath are easily accessible in such a system.

Talking of greenhouses, the Dutch are also working on multi-layer transparent materials which can efficiently splitthe sun's rays into the type of light most useful for plant growth (PAR) and other light that is diverted into electricity production. 

Electricity supplying greenhouses feature an integrated filter on the glass which separates near infrared radiation (NIR), collects it via reflectors and concentrates the radiation into photovoltaic cells. The PAR light is allowed straight through into the greenhouse by the filter system. As this represents less than 50 per cent of total light, there should be less need for cooling of greenhouse interiors in summer.

In the prototype energy-producing greenhouse launched just this summer by the Plant Sciences Group, University of Wageningen, the parabolic NIR reflectors were designed for maximum light concentration. In fact, they concentrated by up to 40 times so that the silicon photovoltaic cells had to be continually cooled. The extra energy produced so far can provide power for greenhouse irrigation, cooling or lighting systems, but can also be sold on to the local electricity network.

"Free" photovoltaic electricity can also power one of the latest robots designed for dairy farms, if required – this time not for milking cows, but for feeding them. Again, we are in the Netherlands. The developer of this latest robot called "Juno" is agricultural engineering company Lely.

Juno, to be launched at the end of this year, is 60 centimetres high, weighs an impressive 575 kilograms and, with its twin electric motors powering three wheels, can push 75-centimetre-high piles of silage closer to the feeding gates. It is being tested in Canada, too, according to Lely.

Juno can be programmed to move up and down the feeding passage regularly through the day and night, pushing the silage up to the feeding cows. And when its power runs low, it simply returns automatically to a recharging point and links up there until its 12-volt batteries are fully charged.

Farmers who've tried the prototype say that hours of fork work can be saved every day. Even more savings will come next year when the Lely robot is to be fitted with a mineral feed metering system, so that the feed can be distributed automatically in the trough or atop the silage as the robot moves down the feed passages.
No information is being given about the price so far. But Lely points out that, where the farmer already produces electricity via photovoltaic cells, then at least Juno's energy input might be free. BF

Norman Dunn writes about European agriculture from Germany.