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ENERGY-BRAZIL: Elephant Grass for Biomass

Mario Osava

RIO DE JANEIRO, Oct 10 2007 (IPS) - Sugarcane is gradually being edged out of pole position for biofuel efficiency, as studies by the Agrobiology Centre at the state Brazilian Agricultural Research Corporation (Embrapa) are finding that elephant grass has even greater potential.

Its dry biomass, burned in ovens, can generate 25 times as much energy as the amount of fossil fuel used to produce it, while sugarcane converted into ethanol only produces nine times as much.

But these two energy balance leaders face different challenges and must travel down different paths before they can compete, for instance, as fuels for electricity generation.

Elephant grass (Pennisetum purpureum) has only recently captured the interest of large energy consumers and companies, after decades of scientific research. It is a cane-like species of grass, brought from Africa at least a century ago and used as cattle fodder. Interest in its possible energy uses was sparked by its high productivity.

The popular eucalyptus tree, planted in Brazil to produce cellulose and charcoal, yields 7.5 tons of dry biomass per hectare a year, on average, and up to 20 tons a year in optimum conditions, while elephant grass yields 30 to 40 tons, Vicente Mazzarella told IPS.

Mazzarella has been studying elephant grass at the Sao Paulo state government’s Institute for Technological Research (IPT) since 1991.

Furthermore, eucalyptus trees take seven years to reach a size worth felling, while elephant grass can be harvested two to four times a year, because of its rapid growth.

And its yield may be increased still further, since the species has hardly been studied and no genetic improvement efforts have yet been carried out. There are close to 200 varieties of elephant grass, and it will take time and effort to identify which ones are best suited to different soil and climate conditions, Mazzarella said.

After 10 years of research, Embrapa’s Agrobiology Centre identified three varieties of elephant grass suited to energy production purposes because of their high yield without nitrogenous fertilisers. For use as a biofuel, the least nutritious varieties are sought, in contrast to its traditional use as animal feed.

The reason is that nutrients like mineral salts produce ash that can damage iron and steel furnaces, Bruno Alves, an agronomist with the elephant grass research team at Embrapa’s Agrobiology Centre, headed by Segundo Urquiaga, told IPS.

That is why tests were done using varieties that grow in poor soil, using the minimum amount of fertilisers, but still producing the highest yields of biomass.

The conversion of energy intake into energy storage (the energy balance) of the plant can be improved by biological nitrogen fixation, in which bacteria take nitrogen from the air and convert it to compounds that fertilise plants.

This is an area in which Embrapa’s Agrobiology Centre has accumulated much expertise in the last few decades, inoculating nitrogen-fixing bacteria into beans and sugarcane.

Biological nitrogen fixation limits itself to the nitrogen required by the plant, avoiding the risk of excessive nitrogenous fertiliser use, said Alves. He pointed out that nitrogenous fertilisers require the greatest amount of fossil fuel energy to produce them chemically, and that by avoiding its use, greenhouse gas emissions are also avoided.

But elephant grass does present certain difficulties. “It likes a lot of water,” so its tolerance of the long dry seasons of the Cerrado, the Brazilian savannah where the largest extensions of land are available for cultivation, must be studied, as well as whether it will maintain its productivity level with less humidity, Alves said.

Drying and compacting the biomass are also a challenge, Mazzarella acknowledged.

Green elephant grass is 80 percent water, and it does not dry out in the sun, as eucalyptus does, but rots if left in piles. To dry, it must be cut up into small pieces, and some heat energy applied. Compacting is necessary for storage and transport because of the great bulk of the dry grass.

The ceramic industry, therefore, is likely to be the first user of elephant grass as an energy source.

Medium-sized ceramic plants require less than 100 hectares of elephant grass grown nearby, which dispenses with compacting and transport. The dried elephant grass can be used in furnaces directly, instead of wood or natural gas. Other processes needing just heat or steam will soon be able to make use of this alternative fuel.

But a medium-sized electricity company, Sykue Bioenergia, has already commissioned a thermoelectric power plant that will be fuelled by elephant grass.

The thermoelectric station will be built in Sao Desiderio in the state of Bahia in northeastern Brazil, by Dedini, an industrial company better known for building sugar mills and distilleries, according to an announcement in July.

The Sykue power plant will cost 80 million reals (43 million dollars) and is due to come onstream in December 2008. It will have a capacity of 30 megawatts and will produce its own elephant grass on a plantation of 4,000 hectares. The company intends to build 10 such power plants and obtain carbon credits for using clean, renewable energy.

Making charcoal from elephant grass, to substitute for coke or traditional charcoal made from wood, still needs further research. But environmental pressures and the threat of an energy deficit in Brazil may accelerate its development and stimulate investment from large steelworks and energy companies.

The potential demand for this alternative energy source is huge, said Mazzarella, who indicated five big markets. As well as steelworks interested in a new charcoal that does not contribute to deforestation, there is a group of large consumers of energy, such as the aluminium industry, the chemical and cement industries, and electricity distributors.

Biomass energy implies a key saving for electricity companies because it can supply extra electricity at times of peak demand, which is the most expensive to produce.

The mining industry, which imports coal to process iron ore into iron and steel for export, could use elephant grass compressed into pellets, similar to wood pellets, in its blast furnaces as an economical and environmentally friendly solution.

In Europe, the use of dry, compacted biomass pellets for heating is growing rapidly, and elephant grass could open up export markets for Brazil similar to those for ethanol, Mazzarella said.