Universitas Helsingiensis

The fruitful union of maize and clover

The fruitful union of maize and cloverBioenergy is hoped to help solve the energy crisis. Researchers in the fields of the Viikki Research Farm are seeking ways to turn these dreams into reality.

Professor of Crop Science Pirjo Mäkelä and Fred Stoddard, university lecturer, are standing ankle-deep in clay. Autumn-withered maize stalks are rustling around them. Amidst the Finnish field and forest scenery, it seems slightly unreal. The south coast of Finland is at such northerly climes that maize plantations are a rare sight even at the Research Farm.

Looking up at the maize, Stoddard is enthusiastic about the success of the maize plantation. They are not testing any genetically modified varieties that are so much debated in Europe now, nor are they trying to find the best maize variety for cold latitudes. This is yet another brouhaha: the bioenergy hype that makes Mäkelä and Stoddard sigh. People are wasting valuable farmland to grow raw material for energy – sometimes even edible produce is used for the purpose.

Flowers in the dumping ground

“Plants for bioenergy should only be cultivated in areas that are unsuitable for food production,” says Fred Stoddard.

“It is often impossible to cultivate edible plants in polluted soil, but our research plants seem to do well with the heavy metals in the soil,” Pirjo Mäkelä says. She is not only talking about areas damaged by pollution accidents. The researchers at

Viikki are very interested in the acid sulphate soils that occur naturally in Finland and contain heavy metals. There is also ongoing research in Viikki into transforming former dumping grounds into bioenergy plantations.

Another big issue is whether bioenergy plantations could be used to enliven the vacating countryside. There is plenty of fallow land in Finland and the rest of Europe.

“We need a cultivation culture where farmers grow plants both for bioenergy and food production. At the same time, the ‘waste’ produced by food production should be exploited more efficiently,” Stoddard says, beckoning towards the nearby lupin field.

Pleasing the bacteria

The lupin is a member of the legume family, which means that it hosts bacteria in its roots. These bacteria have the ability to take nitrogen gas out of the air and convert it into a form of nitrogen usable to the host plant. High in protein content, lupin beans are nutritious – as well as good raw material for silage – and the rest of the plant can be used for bioenergy.

In America, for example, only the grains of maize are currently used, and often in a very inefficient way for ethanol production, Stoddard says. It will be far better when we can use the entire biomass of the plant, each part for its best possible purpose.

Several other legumes are hiding between the maize rows, including faba beans, vetch and clover. “The faba bean has traditionally been grown with maize in China. Our experiments show, however, that maize could also have more suitable partners. Faba beans obviously curb maize growth, whereas together with Persian clover the maize really flourishes,” Stoddard says.

The mixed cultivation of a legume and a grass seems particularly reasonable in the production of biomethane, which is based on fermentation. “Together the two plants create a nutritious mass where the bacteria necessary for methane production thrive,” he says.

All that buzz

One of the blind spots in the current bioenergy hype is the fertilisers used for bioenergy production, Mäkelä and Stoddard say. In Germany, for example, huge amounts of chemicals are thrown on maize fields.

“It is fundamentally absurd and very inefficient. We must find a way to improve the input-output relationship. When studying the kinds of legumes that best suit maize, reed canarygrass or other grasses, we always respect ecological sustainability,” Stoddard says.

Mäkelä and Stoddard together with their colleagues have tested the cultivation of around one hundred plant combinations. According to early results, the best perennial couple is reed canarygrass with goat’s rue or white clover. “Goat’s rue also cleanses oil-polluted soil, which makes it an excellent plant for cultivation,” says Mäkelä, referring to the research results of her colleague Kristina Lindström’s team.

Varieties grown for bioenergy production must always be studied with an open mind, the researchers say. Hemp oil, for instance, is very healthy and hemp fibre can be used in many ways in the textile industry. And the lacy phacelia, growing abundantly in Viikki, provides pollination services for the entire region: “The whole world worried about the mass destruction of bees last summer, but they all just swarmed around our lacy phacelia fields,” Stoddard says with a grin. “I could hear the buzz in my office.”

But the happy buzzing is not a sign of a mission accomplished. Cultivation tests will continue in Viikki next summer, and there will be plenty to do in winter. Having found the best plant combinations, the researchers are now developing the easiest and most energy-efficient cultivation practices to suit them.

Fossil fuels produce new atmospheric carbon dioxide, but the idea behind bioenergy is to absorb the existing carbon dioxide from the atmosphere. “The profitability calculation must include the entire cultivation process with direct and indirect carbon dioxide streams,” Stoddard says.

Virve Pohjanpalo

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