• Authors:
    • Astrup, T.
    • Wenzel, H.
    • Hamelin, L.
    • Tonini, D.
  • Source: Environmental Science & Technology
  • Volume: 46
  • Issue: 24
  • Year: 2012
  • Summary: In the endeavor of optimizing the sustainability of bioenergy production in Denmark, this consequential life cycle assessment (LCA) evaluated the environmental impacts associated with the production of heat and electricity from one hectare of Danish arable land cultivated with three perennial crops: ryegrass (Lolium perenne), willow (Salix viminalis) and Miscanthus giganteus. For each, four conversion pathways were assessed against a fossil fuel reference: (I) anaerobic co-digestion with manure, (II) gasification, (III) combustion in small-to-medium scale biomass combined heat and power (CHP) plants and IV) co-firing in large scale coal-fired CHP plants. Soil carbon changes, direct and indirect land use changes as well as uncertainty analysis (sensitivity, MonteCarlo) were included in the LCA. Results showed that global warming was the bottleneck impact, where only two scenarios, namely willow and Miscanthus co-firing, allowed for an improvement as compared with the reference (-82 and -45 t CO2-eq. ha(-1), respectively). The indirect land use changes impact was quantified as 310 + 170 t CO2-eq. ha(-1), representing a paramount average of 41% of the induced greenhouse gas emissions. The uncertainty analysis confirmed the results robustness and highlighted the indirect land use changes uncertainty as the only uncertainty that can significantly change the outcome of the LCA results.
  • Authors:
    • Wiegel, R.
    • Claupein, W.
    • Graeff-Hoenninger, S.
    • Butterbach-Bahl, K.
    • Gauder, M.
  • Source: Web Of Knowledge
  • Volume: 4
  • Issue: 3
  • Year: 2012
  • Summary: Willow coppice, energy maize and Miscanthus were evaluated regarding their soil-derived trace gas emission potential involving a nonfertilized and a crop-adapted slow-release nitrogen (N) fertilizer scheme. The N application rate was 80 kg N ha-1 yr-1 for the perennial crops and 240 kg N ha-1 yr-1 for the annual maize. A replicated field experiment was conducted with 1-year measurements of soil fluxes of CH4, CO2 and N2O in weekly intervals using static chambers. The measurements revealed a clear seasonal trend in soil CO2 emissions, with highest emissions being found for the N-fertilized Miscanthus plots (annual mean: 50 mg C m-(2) h-1). Significant differences between the cropping systems were found in soil N2O emissions due to their dependency on amount and timing of N fertilization. N-fertilized maize plots had highest N2O emissions by far, which accumulated to 3.6 kg N2O ha-1 yr-1. The contribution of CH4 fluxes to the total soil greenhouse gas subsumption was very small compared with N2O and CO2. CH4 fluxes were mostly negative indicating that the investigated soils mainly acted as weak sinks for atmospheric CH4. To identify the system providing the best ratio of yield to soil N2O emissions, a subsumption relative to biomass yields was calculated. N-fertilized maize caused the highest soil N2O emissions relative to dry matter yields. Moreover, unfertilized maize had higher relative soil N2O emissions than unfertilized Miscanthus and willow. These results favour perennial crops for bioenergy production, as they are able to provide high yields with low N2O emissions in the field.
  • Authors:
    • Negri, M. C.
    • Gopalakrishnan, G.
    • Salas, W.
  • Source: GCB Bioenergy
  • Volume: 4
  • Issue: 6
  • Year: 2012
  • Summary: Current research on the environmental sustainability of bioenergy has largely focused on the potential of bioenergy crops to sequester carbon and mitigate greenhouse gas emissions and possible impacts on water quality and quantity. A key assumption in these studies is that bioenergy crops will be grown in a manner similar to current agricultural crops such as corn and hence would affect the environment similarly. In this study, we investigate an alternative cropping system where bioenergy crops are grown in buffer strips adjacent to current agricultural crops such that nutrients present in runoff and leachate from the traditional row-crops are reused by the bioenergy crops (switchgrass, miscanthus and native prairie grasses) in the buffer strips, thus providing environmental services and meeting economic needs of farmers. The process-based biogeochemical model Denitrification-Decomposition (DNDC) was used to simulate crop yield, nitrous oxide production and nitrate concentrations in leachate for a typical agricultural field in Illinois. Model parameters have been developed for the first time for miscanthus and switchgrass in DNDC. Results from model simulations indicated that growing bioenergy crops in buffer strips mitigated nutrient runoff, reduced nitrate concentrations in leachate by 60-70% and resulted in a reduction of 50-90% in nitrous oxide emissions compared with traditional cropping systems. While all the bioenergy crop buffers had significant positive environmental benefits, switchgrass performed the best with respect to minimizing nutrient runoff and nitrous oxide emissions, while miscanthus had the highest yield. Overall, our model results indicated that the bioenergy crops grown in these buffer strips achieved yields that are comparable to those obtained for traditional agricultural systems while simultaneously providing environmental services and could be used to design sustainable agricultural landscapes.
  • Authors:
    • Schwarz, G.
    • Noleppa, S.
    • Kern, M.
  • Source: Pest Management Science
  • Volume: 68
  • Issue: 11
  • Year: 2012
  • Summary: BACKGROUND: A major global challenge is to provide agricultural production systems that are able to sustain growing demands for food, feed, fibre and renewable raw materials without exacerbating climate change. Detailed and reliable data on the CO2 balance of different agricultural management activities and inputs as a basis to quantify carbon footprints of agriculture are still lacking. This study aims to fill this gap further by quantifying the net balance of emitted and assimilated CO2 due to the application of crop protection treatments on the farm, and by assessing their partial contribution to GHG emissions and mitigation in agriculture. The study focuses on key agricultural crops including wheat, corn, oilseeds and sugar crops. RESULTS: The final CO2 balance, considering GHG emissions due to on-farm CPP treatment in comparison with CO2 storage in additional biomass, CO2 protected with respect to agrotechnical inputs and land inputs and CO2 saved with respect to associated global land use changes, is positive and may reach multiples of up to nearly 2000. CONCLUSION: The results highlight the importance of the positive yield effects of the CPP programme applications on the farm, resulting in additional assimilated biomass at the farm level and less land use changes at the global level, and thus lower pressure on environmentally important indicators of overall agricultural sustainability.
  • Authors:
    • Schoene, D.
    • Lobovikov, M.
    • Yping, L.
  • Source: Mitigation and Adaptation Strategies for Global Change
  • Volume: 17
  • Issue: 3
  • Year: 2012
  • Summary: Climate change negotiations, assessments, and greenhouse gas inventory guidelines have all but bypassed bamboo. Disallowing stands of tree-like bamboos as forests disparages their function in the carbon (C) cycle, and disregards pillars of smallholder livelihoods. Exposing bamboo not as a panacea, but as an overlooked option for C conservation, sequestration, and adaptation, we screen details of distribution, morphology, growth, physiology, and impacts for pertinence to climate change. Additional to 40 million hectares of existing bamboo forests, many potential host countries for C projects harbor suitable sites. Definitions, methods and default values, such as the root/shoot- ratio, biomass conversion factors, allometric equations and sampling variables need adjusting. Rapid maturation, persistent rhizomes, a rich palette of species, and wind-firmness may mitigate risk. Bamboos can accommodate agro-and urban forestry, and reign in unsustainable shifting cultivation. Distribution functions of bamboo biomass stocks and growths do not deviate drastically from those of trees. If anything, bamboo stocks are slightly lower, and growths slightly higher, with medians of 87 t*ha(-1) and 10.5 t*ha(-1)*yr(-1), respectively. However, bamboo's outstanding socio-economic effects might well determine its future in mitigation and adaptation. Early, continuous yields, selective harvesting on even small parcels of land, low capital and high labor intensity, virtually 100% conversion efficiency to about 1,500 products, and, typically, 75% of economic returns benefiting rural people are advantageous attributes. Regional studies on suitability, silviculture, yields, economics, risk, and C assessment would strengthen bamboo's function as 'the poor man's timber' and promote its niche as the smallholder's C sink.
  • Authors:
    • Ostonen, I.
    • Aavola, R.
    • Soosaar, K.
    • Maddison, M.
    • Jaerveoja, J.
    • Mander, U.
    • Salm, J.
  • Source: GCB Bioenergy
  • Volume: 4
  • Issue: 4
  • Year: 2012
  • Summary: We studied the impact of reed canary grass (RCG) cultivation on greenhouse gas emission in the following sites of an abandoned peat extraction area in Estonia: a bare soil (BS) site, a nonfertilized Phalaris (nfP) plot, a fertilized Phalaris (fP) plot, and a natural bog (NB) and a fen meadow (FM) as reference areas. The C balance and global warming potential (GWP) were estimated by measuring CO2, CH4, and N2O emissions and aboveground and belowground biomass variations. The high CO2 flux from the nfP and fP sites and the low CO2 emission from the BS are due to the enhancement of mineralization by plant growth on planted sites and inhibited mineralization by the recalcitrant C of BS. The NB site emitted 24 kg CH4 ha(-1) yr(-1), whereas the almost zero CH4 emission from the Phalaris plots and the BS site was due to the high S concentration in peat, which probably inhibited methanogenesis. The N2O flux varied from <0.1 kg on the Phalaris plots and the NB to 2.64 kg N2O ha(-1) yr(-1) on the FM. The highest yield of RCG was obtained in autumn (13.9 t and 8.0 t dw ha(-1) on the fP and nfP, respectively). By spring, the biomass yield on the fP and nfP plot was 12.7 and 7.9 t dw ha(-1), respectively. The C balance of nfP and fP plots was negative in comparison to the BS (-3322, -5983, and 2504 kg CO2 ha(-1) yr(-1), respectively). This indicates that the cultivation of RCG transformed them from a net source of C into a net sink of C. The GWP for the fP and nfP sites was -5981 and -3885 kg CO2 eq ha(-1) yr(-1), respectively. The BS site had a total GWP of 2544 kg CO2 eq ha(-1) yr(-1).
  • Authors:
    • Venslauskas, K.
    • Zuperka, V.
    • Kulikauskas, T.
    • Nekrosius, A.
    • Navickas, K.
  • Source: Proceedings of the 10th International Scientific Conference, Engineering for Rural Development, Jelgava, Latvia
  • Year: 2011
  • Summary: The energy balance of biogas production from perennial grass silage has been investigated in this paper. The anaerobic digestion process parameters and grass species have influence on biogas yield such as organic load. The model of technological process of biomass preparation and its digestion to biogas has been performed. The variation of digester organic load (1.0; 1.5 and 2.0 kg VS.m -3.d -1) shows the difference in total (direct and indirect) energy input from 490 MJ.t -1 biomass at 2.0 kg VS.m -3.d -1 up to 570 MJ.t -1 biomass at 1.0 kg VS.m -3.d -1. The laboratory experiments of biogas production from grass silage show the highest biogas yield (115 l.kg -1 biomass) at 1.0 kg VS.m -3.d -1. By increasing the organic load up to 2.0 kg VS.m -3.d -1 the biogas yield decreases down to 93 l.kg -1 from biomass. The methane (CH 4) concentration in the obtained biogas had a little dependence on digester organic load and was in the range of 58-60%. Such biogas has a sufficient methane concentration and is suitable for cogeneration.
  • Authors:
    • Poje, T.
  • Source: SAD, Revija za Sadjarstvo, Vinogradnistvo in Vinarstvo
  • Volume: 22
  • Issue: 1
  • Year: 2011
  • Summary: Spreading organic fertilizers in perennial plantations, such as vineyards and orchards, by mechanical means is discussed, and the different basic types of manure spreader suited to this operation are described.
  • Authors:
    • Preez, C.
    • Huyssteen, C.
    • Mnkeni, P.
  • Source: South African Journal of Science
  • Volume: 107
  • Issue: 5/6
  • Year: 2011
  • Summary: The decline of soil organic matter as a result of agricultural land use was identified for a review with the ultimate aim of developing a soil protection strategy and policy for South Africa. Such a policy is important because organic matter, especially the humus fraction, influences the characteristics of soil disproportionately to the quantities thereof present. Part 1 of this review dealt with the spatial variability of soil organic matter and the impact of grazing and burning under rangeland stock production. In this second part of the review, the impact of arable crop production on soil organic matter is addressed. A greater number of studies have addressed the degradation of soil organic matter that is associated with arable crop production than the restoration. However, cropping under dryland has been found to result in significant losses of soil organic matter, which is not always the case with cropping under irrigation. Restoration of soil organic matter has been very slow upon the introduction of conservational practices like zero tillage, minimal tillage, or mulch tillage. Reversion of cropland to perennial pasture has also been found to result in discouragingly slow soil organic matter restoration. Although increases or decreases in soil organic matter levels have occurred in the upper 300 mm, in most instances this took place only in the upper 50 mm. The extent of these changes was dependent inter alia on land use, soil form and environmental conditions. Loss of soil organic matter has resulted in lower nitrogen and sulphur reserves, but not necessarily lower phosphorus reserves. Depletion of soil organic matter coincided with changes in the composition of amino sugars, amino acids and lignin. It also resulted in a decline of water stable aggregates which are essential in the prevention of soil erosion. Although much is known about how arable crop production affects changes in soil organic matter, there are still uncertainties about the best management practices to maintain and even restore organic matter in degraded cropland. Coordinated long-term trials on carefully selected ecotopes across the country are therefore recommended to investigate cultivation practices suitable for this purpose.
  • Authors:
    • Santos, H.
    • Fontaneli, R.
    • Spera, S.
    • Dreon, G.
  • Source: Revista Brasileira de Ciencias Agrarias
  • Volume: 6
  • Issue: 3
  • Year: 2011
  • Summary: Soil fertility attributes were evaluated on a typical dystrophic Red Latosol (typic Haplorthox) located in Passo Fundo, State of Rio Grande do Sul, Brazil, twelve years after the establishment (1993, 2000, 2002 and 2005) of five integrated crop/livestock farming production systems: system I - wheat/soybean, white oat/soybean, and common vetch/corn; system II - wheat/soybean, white oat/soybean, and grazed black oat+grazed common vetch/corn; system III - perennial cool season pastures (fescue+white clover+red clover+birds foot trefoil); system IV - perennial warm season pastures (bahiagrass+black oat+rye grass+white clover+red clover+birds foot trefoil); and system V - alfalfa as hay crop. The plots under systems III, IV, and V returned to system I after the summer of 1996. However, in the summer of 2002, in the systems III, IV and V, what used to be crop returned to pasture and what used to be pasture returned to crop. An acidification process occurred in all layers by the lowest pH values and higher concentration and saturation by Al, in comparison to the soil in 1998. The organic matter level and the P, K and Al levels increased between 1998 to 2002, in all sampled layers, while the opposite occurred with pH, Ca and Mg contents.