The EU’s climate and energy package has laid down that the member countries of EU must, by 2020, have reduced their greenhouse gas emissions by 20 per cent and increased the use of biogas to 10 per cent. This requires new investments even from countries such as Sweden which has a relatively high, but not sufficient, supply of renewable energy. In the short and medium term, a large proportion of the growth potential is to be found in agriculture and forestry. This must however be compatible with the national environmental objectives such as only natural acidification, a rich plant and animal life, sustainable forests and a rich farming landscape. Apart from direct conversions of the energy systems, there are relatively large opportunities for energy effectivisation in different sectors of society, inter alia in agriculture and forestry.
The research programmes of SLU in the fields of energy and climate deal with different aspects of these issues. The starting point for all bioenergy use is that it must be climate neutral. This means that when new crops are grown to replace that which has been used for energy purposes, as much carbon shall be sequestrated as that used. Obviously, input energy will be a cost. It is also obvious that the time for the restoration of the carbon store varies depending on the type of crop involved; annual farming crops - short time, 1 year; energy forests – a little longer, 4-6 years; forests – a long time, 50-100 years.
SLU’s research on energy forests, salix, has been going on for several decades. During this time the yield of willow has increased by more than 50 per cent. In a large thematic project that extends over molecular biology, ecophysiology and field experiments, the researchers are working to further increase and secure production. Photographer: Pär Aronsson
The important properties to be developed in willow are resistance against rusts and leaf beetles, since attack by these reduces production. Varieties of willow that are resistant to frost and drought are also sought. Demand for willow will probably grow as Europe is endeavouring to comply with the climate policy requirements.
System studies
The optimisation of energy utilisation demands knowledge at system level. Ideally, such studies should consider both economic and environmental goals and the social aspects of the choice and production of energy crops. At the SLU Department of Energy and Technology, Per-Anders Hansson and his research team are engaged on system studies of agricultural energy use. The applied objective is to find possible energy savings at all stages of the tilling and cultivation of agricultural land, as well as in transport chains and the processing of the crop.
Postgraduate students Serina Ahlgren and Marie Kimming are working just now (May 2009) on a government commission to calculate the emissions of greenhouse gases from the growing of crops for biofuel production. The calculations are made in accordance with the RES (Renewable Energy Sources) Directive of the EU. This lays down limiting values for greenhouse gas emissions that must not be exceeded for various crops if it is to be permissible for these crops to be used for the production of vehicle fuels. The preliminary calculations of SLU show that the critical factor is the quantity of nitrous oxide that the cultivation generates. The production of nitrous oxide from the ground under different conditions is difficult to determine in field measurements and models.
The Swedish Energy Agency has given Åsa Kasimir-Klemedtsson, Göteborg University, a special commission to compile the state of knowledge in this area. Calculations from SLU, as well as studies from other places, show that biogas is a very advantageous option from the standpoint of the climate. Biogas production from manure provides a dual gain. It replaces fossil fuels and the residues from the burning of biogas are less potent greenhouse gases than the methane which would otherwise have been released from the manure.
Microbiology
In the project MicroDrive (Microbially Derived Energy), Johan Schnürer of the Department of Microbiology, SLU, and his colleagues are working on a recycling system for the production of ethanol and biogas. Here, ethanol is produced from plant cellulose. The grain fermentation residues from ethanol production are digested into biogas. The digestion residues from biogas production are, in turn, used as fertiliser for the crop that will be fermented into ethanol. One focus in the project is on the development of microorganisms and enzyme systems which effectively break down the cellulose during the generation of alcohol. Apart from microbiologists, molecular biologists Mats Sandgren and Jerry Ståhlberg are also conducting studies into the capacity and efficacy of enzymes. MicroDriveE at SLU is running an “exjob-school” on the model of the researcher schools for postgraduate students.
MicroDrive – production of ethanol and biogas in a recycling system.
Energy forests
SLU’s research on energy forests, salix, has been going on for several decades. During this time the yield of willow has increased by more than 50 per cent. In a large thematic project that extends over molecular biology, ecophysiology and field experiments, the researchers are working to further increase and secure production. Molecular geneticists are engaged on finding genetic markers for important properties which are developed through traditional plant breeding. The important properties to be developed in willow are resistance against rusts and leaf beetles, since attack by these reduces production. Varieties of willow that are resistant to frost and drought are also sought. Demand for willow will probably grow as Europe is endeavouring to comply with the climate policy requirements. The thematic project on willows is coordinated by Sara von Arnold, Department of Plant Biology and Forest Genetics.
Stumps, branches and crowns
By far the highest proportion of the bioenergy utilised at present comes from conventional forestry. It is branches and crowns from felling that are used, and also the energy content of black liquor residues from the pulp industry. In recent years, stump extraction has also been used as a source to increase the supply of bioenergy raw materials.
At the Department of Ecology, several research teams are investigating the environmental impacts of forest fuel harvesting. Riita Hyvönen and Göran Ågren have shown in model calculations that the losses of soil-bound carbon which may be the consequence of forest fuel harvesting are fairly marginal. When the fossil fuel that forest fuel replaces is deducted, biofuel from the forest clearly produces a reduction in greenhouse gas emissions. All growing crops make the soil acid, while degradation of dead plant residues, together with the weathering of minerals, returns neutralising substances into the soil. When branches and crowns are removed, the risk of soil acidification increases, as Bengt Olsson and others have shown in their studies. Soil acidification and the removal of certain plant nutrients can be compensated for by returning to the forest the wood ash from heating plants fired by forest fuel. The ash is treated, hardened and crushed, so that it is not dissolved too rapidly in the soil but produces an extended effect. The properties of ash and its effect on the soil and vegetation are also studied by research teams at SLU. Research on the processing of tree fuels, through the production of pellets for direct burning or for gasification into biofuels, is in progress at the Unit for Biomass Technology and chemistry at SLU in Umeå.
Bioenergy contributes approximately 25% of the energy that is annually used in Sweden. Hydroelectric and nuclear power each produce about half of this, if heat losses from nuclear plants are ignored. (According to Energy Report 2008).
Stump extraction
About 20 per cent of the biomass of conifers is in the stump. Up to now, this resource has been practically unused in bioenergy contexts. In view of the increasing demand for raw materials, stump extraction has now begun. Together with the Energy Agency and the forest industry, SLU is now funding a thematic project on the positive and negative environmental impacts of stump extraction. The objective is that by next year a scientific base should be available for a broad environmental analysis which, in turn, can give recommendations on where stumps can be extracted and the environments that are to be saved from stump harvesting so as to cause the least possible environmental impact. Issues of biodiversity are especially important in connection with stumps and the stock of aging dead wood in the forest.
The Energy Agency is conducting most of its r&d into biofuel in a coordinated programme “Sustainable production and processing of biofuels”. This programme funds a very large proportion of Swedish research in this area, inter alia the projects at SLU. Work is carried out both as individual projects and also in the form of major programmes that are co-funded by industry.
Author
:
Helene Lundkvist
is Professor of Soil Ecology and is engaged on the coordination of energy and climate research at SLU