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Molinuevo-Salces B.,University of Aalborg | Larsen S.U.,AgroTech Institute for Agri Technology and Food Innovation | Ahring B.K.,University of Aalborg | Ahring B.K.,Washington State University | Uellendahl H.,University of Aalborg
Biomass and Bioenergy

The combination of catch crop cultivation with its use for biogas production would increase renewable energy production in the form of methane, without interfering with the production of food and fodder crops. The low biomass yield of catch crops has been shown as the main limiting factor for using these crops as co-substrate in biogas plants, since the profit obtained from the sale of methane barely compensates the harvest costs. Therefore, a new agricultural strategy to harvest catch crops together with the residual straw of the main crop was investigated, in order to increase the biomass and the methane yield per hectare. Seven catch crops harvested together with stubble from the previous main crop were evaluated. The effects of stubble height, harvest time and ensiling as a storage method for the different catch crops/straw blends were studied. Biomass yields as TS ranged between 3.2 and 3.6 t ha-1 y-1 of which the catch crop constituted around 10% of the total biomass yield. Leaving the straw on the field until harvest of the catch crop in the autumn could benefit methane production from the straw both due to increased biomass yield and an increased organic matter bioavailability of the straw taking place on the field during the autumn months. Ensiling as a storage method could be feasible in terms of energy storage and guaranteeing the feedstock availability for the whole year. This new agricultural strategy may be a good alternative for economically feasible supply of catch crops and straw for biogas production. Source

Feilberg A.,University of Aarhus | Nyord T.,University of Aarhus | Hansen M.N.,AgroTech Institute for Agri Technology and Food Innovation | Lindholst S.,Danish Technological Institute DTI
Journal of Environmental Quality

Field application of animal manure is a major cause of odor nuisance in the local environment. Therefore, there is a need for methods for measuring the effect of technologies for reducing odor after manure application. In this work, chemical methods were used to identify key odorants from field application of pig manure based on experiments with surface application by trailing hoses and soil injection. Results from three consecutive years of field trials with full-scale equipment are reported. Methods applied were: membrane inlet mass spectrometry (MIMS), proton-transfer-reaction mass spectrometry (PTR- MS), gold-film hydrogen sulfide (H 2S) detection, all performed on site, and thermal desorption gas chromatography with mass spectrometry (TD-GC/MS) based on laboratory analyses of field samples. Samples were collected from a static flux chamber often used for obtaining samples for dynamic olfactometry. While all methods were capable of detecting relevant odorants, PTR-MS gave the most comprehensive results. Based on odor threshold values, 4-methylphenol, H 2S, and methanethiol are suggested as key odorants. Significant odorant reductions by soil injection were consistently observed in all trials. The flux chamber technique was demonstrated to be associated with critical errors due to compound instabilities in the chamber. This was most apparent for H 2S, on a time scale of a few minutes, and on a longer time scale for methanethiol. © 2011 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. Source

Larsen S.U.,University of Aarhus | Larsen S.U.,AgroTech Institute for Agri Technology and Food Innovation | Jorgensen U.,University of Aarhus | Kjeldsen J.B.,University of Aarhus | Laerke P.E.,University of Aarhus
Bioenergy Research

Long-term yield studies in perennial crops like miscanthus are important to determine mean annual energy yield and the farmer's economy. In two Danish field trials, annual yield of two miscanthus genotypes was followed over a 20-year period. The trials were established in 1993 on loamy sand in Foulum and on coarse sand in Jyndevad. Effects of genotype, row distance and fertilization were investigated. In both trials, yield development over time was characterized by an increase during the first years, optimum yields after 7-8 years and a decrease to a lower level which remained relatively constant from year 11 to 20. Spring harvest reduced the yield by 34-42 % compared to autumn harvest. In Foulum annual fertilization with 75 kg ha-1 N increased the yield of the genotype Goliath (Miscanthus sinensis) by 26 %. Additional N fertilization only increased the yield of Goliath little, and the genotype Giganteus (Miscanthus × giganteus) did not respond to fertilization at all. The highest mean yield in Foulum for the period 1997-2012 was obtained with the shortest row distance (~18,000 rather than ~12,000 plants ha-1) and harvested in late autumn, namely 13.1 and 12.0 Mg ha-1 DM annually for Giganteus and Goliath, respectively. In Jyndevad, where only Goliath was studied, the highest yield during 1995-2001 was obtained by short row distance, autumn harvest and annual fertilization with 75 kg ha-1 N, with yield increasing up to 116 % in response to fertilization. A mean yield of 14.4 Mg ha-1 DM was achieved over the period 1995-2012. © 2013 Springer Science+Business Media New York. Source

Larsen S.U.,University of Aarhus | Larsen S.U.,AgroTech Institute for Agri Technology and Food Innovation | Jorgensen U.,University of Aarhus | Kjeldsen J.B.,University of Aarhus | Laerke P.E.,University of Aarhus
Biomass and Bioenergy

A prerequisite for successful willow production is a reliable and economically competitive establishment of the crop. Here, we compare different establishment methods including long-term yield effects. A field trial with the new-bred variety Bjørn was established in 1996 and included four establishment methods; 1) vertical planting of standard 0.2m cuttings; 2) horizontal planting of 0.1m billets; 3) horizontal planting of 0.2m billets; 4) horizontal planting of 1.8m rods. All establishment methods were combined with mechanical and chemical weed control during the establishment year. Dry matter (DM) yield was measured over 6 harvest rotations corresponding to 16 years. In 1st rotation, yield differed significantly between establishment methods with highest yield for 1.8m rods (10.4Mgha-1 year-1), intermediate yield for cuttings and 0.2m billets (8.6 and 8.5Mgha-1 year-1, respectively) and lowest for 0.1m billets (5.6Mgha-1 year-1). No differences were found in 2nd rotation. Over 1st and 2nd rotation, mechanical weed control resulted in significantly lower yield than chemical control when combined with 0.1m billets. Cuttings and 1.8m rods were compared over 1st, 2nd, 3rd, 5th and 6th rotation. Rods gave higher yield in 1st rotation, lower yield in 3rd rotation but there were no significant yield differences in 2nd, 5th and 6th rotations, resulting in similar mean yields of 12.4 and 11.9Mgha-1 year-1 for cuttings and rods over the whole period. The general yield development over time indicates a relatively stable long-term yield level. © 2014 Elsevier Ltd. Source

Larsen S.U.,AgroTech Institute for Agri Technology and Food Innovation | Bruun S.,Copenhagen University | Lindedam J.,Copenhagen University
Biomass and Bioenergy

Straw is a by-product from cereal production which constitutes a considerable biomass resource, for instance for 2G ethanol production. Straw yield per hectare and straw quality in terms of ethanol production are both important factors for the available biomass resource and the potential ethanol production per hectare. In a series of field trials on three locations in 2009, we compared straw and grain yield from the winter cereal species triticale, winter barley, winter rye, and winter wheat. Grain yield did not differ significantly between the species, but winter rye yielded up to 59% more straw dry matter than the other species. The release of glucose and xylose after pretreatment and enzymatic hydrolysis i.e. the saccharification potential was used to indicate the potential for ethanol production. The saccharification potential did not differ between species, but due to the differences in straw yield, areal saccharification potential (i.e. potential sugar production per hectare) was from 29% to 78% higher for winter rye than for other species. In a series of winter wheat cultivar trials on two locations in 2008 and three locations in 2009, straw yield differed significantly between cultivars in both years and across years. The highest yielding cultivar yielded up to 57% and 37% more straw than the lowest yielding cultivar in the two years, respectively, even among cultivars with non-significant differences in grain yield. The saccharification potential was measured from straw of winter wheat cultivar trials harvested in 2009. The potential varied largely but was not significantly affected by neither cultivar nor location. Due to cultivar differences in straw yield, however, areal saccharification potential differed significantly between cultivars with up to 38% difference in glucose yield and up to 35% in xylose yield. Straw yield increased with increasing grain yield, but the straw:grain ratio differed significantly between cultivars and was not consistent across years and locations. This has implications for straw resource estimates when these are based on the relationship between grain yield and straw yield. In conclusion, it appears possible to choose species and cultivars with higher straw yield and consequently larger potential for ethanol production per hectare without compromising grain yield. This may provide a means of increasing the overall straw resource, as long as increased straw yield is not accompanied by negative effects such as increased tendency to lodging. © 2012 Elsevier Ltd. Source

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