• Authors:
    • Zegada-Lizarazu, W.
    • Walter, K.
    • Valentine, J.
    • Djomo, S. Njakou
    • Monti, A.
    • Mander, U.
    • Lanigan, G. J.
    • Jones, M. B.
    • Hyvonen, N.
    • Freibauer, A.
    • Flessa, H.
    • Drewer, J.
    • Carter, M. S.
    • Skiba, U.
    • Hastings, A.
    • Osborne, B.
    • Don, A.
    • Zenone, T.
  • Source: GCB Bioenergy
  • Volume: 4
  • Issue: 4
  • Year: 2012
  • Summary: Bioenergy from crops is expected to make a considerable contribution to climate change mitigation. However, bioenergy is not necessarily carbon neutral because emissions of CO2, N2O and CH4 during crop production may reduce or completely counterbalance CO2 savings of the substituted fossil fuels. These greenhouse gases (GHGs) need to be included into the carbon footprint calculation of different bioenergy crops under a range of soil conditions and management practices. This review compiles existing knowledge on agronomic and environmental constraints and GHG balances of the major European bioenergy crops, although it focuses on dedicated perennial crops such as Miscanthus and short rotation coppice species. Such second-generation crops account for only 3% of the current European bioenergy production, but field data suggest they emit 40% to >99% less N2O than conventional annual crops. This is a result of lower fertilizer requirements as well as a higher N-use efficiency, due to effective N-recycling. Perennial energy crops have the potential to sequester additional carbon in soil biomass if established on former cropland (0.44 Mg soil C ha(-1) yr(-1) for poplar and willow and 0.66 Mg soil C ha(-1) yr(-1) for Miscanthus). However, there was no positive or even negative effects on the C balance if energy crops are established on former grassland. Increased bioenergy production may also result in direct and indirect land-use changes with potential high C losses when native vegetation is converted to annual crops. Although dedicated perennial energy crops have a high potential to improve the GHG balance of bioenergy production, several agronomic and economic constraints still have to be overcome.
  • Authors:
    • Skiba, U.
    • Baggs, E. M.
    • Lloyd, C. R.
    • Finch, J. W.
    • Drewer, J.
  • Source: GCB Bioenergy
  • Volume: 4
  • Issue: 4
  • Year: 2012
  • Summary: It is important to demonstrate that replacing fossil fuel with bioenergy crops can reduce the national greenhouse gas (GHG) footprint. We compared field emissions of nitrous oxide (N2O), methane (CH4) and soil respiration rates from the C-4 grass Miscanthus x giganteus and willow (salix) with emissions from annual arable crops grown for food production. The study was carried out in NE England on adjacent fields of willow, Miscanthus, wheat (Triticum aetivum) and oilseed rape (Brassica napus). N2O, CH4 fluxes and soil respiration rates were measured monthly using static chambers from June 2008 to November 2010. Net ecosystem exchange (NEE) of carbon dioxide (CO2) was measured by eddy covariance on Miscanthus from May 2008 and on willow from October 2009 until November 2010. The N2O fluxes were significantly smaller from the bioenergy crops than that of the annual crops. Average fluxes were 8 and 32 mu g m(-2) h(-1) N2O-N from wheat and oilseed rape, and 4 and 0.2 mu g m(-2) h(-1) N2O-N from Miscanthus and willow, respectively. Soil CH4 fluxes were negligible for all crops and soil respiration rates were similar for all crops. NEE of CO2 was larger for Miscanthus (-770 g C m(-2) h(-1)) than willow (-602 g C m(-2) h(-1)) in the growing season of 2010. N2O emissions from Miscanthus and willow were lower than for the wheat and oilseed rape which is most likely a result of regular fertilizer application and tillage in the annual arable cropping systems. Application of N-15-labelled fertilizer to Miscanthus and oil seed rape resulted in a fertilizer-induced increase in N2O emission in both crops. Denitrification rates (N2O + N-2) were similar for soil under Miscanthus and oilseed rape. Thus, perennial bioenergy crops only emit less GHGs than annual crops when they receive no or very low rates of N fertilizer.
  • Authors:
    • Dyer,Lisa
    • Oelbermann,Maren
    • Echarte,Laura
  • Source: Journal of Plant Nutrition and Soil Science
  • Volume: 175
  • Issue: 3
  • Year: 2012
  • Summary: The Argentine Pampa is one of the major global regions for the production of maize (Zea mays L.) and soybean (Glycine max L. [Merr.]), but intense management practices have led to soil degradation and amplified greenhouse-gas (GHG) emissions. This paper presents preliminary data on the effect of maize-soybean intercrops compared with maize and soybean sole crops on the short-term emission rates of CO2 and N2O and its relationship to soil moisture or temperature over two field seasons. Soil organic carbon (SOC) concentrations were significantly greater (p < 0.05) in the maize sole crop and intercrops, whereas soil bulk density was significantly lower in the intercrops. Soil CO2 emission rates were significantly greater in the maize sole crop but did not differ significantly for N2O emissions. Over two field seasons, both trace gases showed a general trend of greater emission rates in the maize sole crop followed by the soybean sole crop and were lowest in the intercrops. Linear regression between soil GHG (CO2 and N2O) emission rates and soil temperature or volumetric soil moisture were not significant except in the 1:2 intercrop where a significant relationship was observed between N2O emissions and soil temperature in the first field season and between N2O and volumetric soil moisture in the second field season. Our results demonstrated that intercropping in the Argentine Pampa may be a more sustainable agroecosystem land-management practice with respect to GHG emissions.
  • Authors:
    • Olander, L. P.
    • Eagle, A. J.
  • Source: Advances in Agronomy
  • Volume: 115
  • Year: 2012
  • Summary: Responsible for 6% of U.S. greenhouse gas (GHG) production, agricultural land use has significant potential to reduce these emissions and capture additional carbon in the soil. Many different activities have been proposed for such mitigation, but assessments of the biophysical potential have been limited and have not provided direct comparison among the many options. We present an in-depth review of the scientific literature, with a side-by-side comparison of net biophysical GHG mitigation potential for 42 different agricultural land management activities in the United States, many of which are likely applicable in other regions. Twenty of these activities are likely to be beneficial for GHG mitigation and have sufficient research to support this conclusion. Limited research leads to uncertainty for 15 other activities that may have positive mitigation potential, and the remaining activities have small or negative GHG mitigation potential or life-cycle GHG concerns. While we have sufficient information to move forward in implementing a number of activities, there are some high-priority research needs that will help clarify problematic uncertainties.
  • Authors:
    • Emmerling, C.
    • Felten, D.
  • Source: Journal of Plant Nutrition and Soil Science
  • Volume: 175
  • Issue: 5
  • Year: 2012
  • Summary: Bioenergy is becoming an important option in Global Change mitigation policy world-wide. In agriculture, cultivation of energy crops for biodiesel, biogas, or bioethanol production received considerable attention in the past decades. Beyond this, the cultivation of Miscanthus, used as solid fuel for combustion, may lead to an increase in soil organic matter content compared to other agricultural land use, since C-sequestration potential in soils of Miscanthus crops is high due to, e.g., high amounts of harvest residues. This may indirectly contribute to a reduction of atmospheric CO2 concentration. The objective of the present work was to investigate the development of soil organic carbon and Miscanthus-derived C contents, as well as to estimate carbon stocks in soils cultivated with Miscanthus using 13C-natural-abundance technique. The investigations were carried out in relation to soil depth up to 150?cm in a sequence of 2, 5, and 16 y of cultivation relative to a reference soil cultivated with cereals. Amounts of total organic C (TOC) and Miscanthus-derived C (Miscanthus-C) increased with increasing duration of cultivation. For example, TOC increased from 12.8 to 21.3 g C?kg1 after 16 y of cultivation at the depth of 015?cm, whereby the portion of Miscanthus-C reached 5.8 g C?kg1. Also within deeper soil layers down to 60?cm depth a significant enhancement of Miscanthus-C was detectable even though TOC contents were not significantly enhanced. At soil depth below 60?cm, no significant differences between treatments were found for Miscanthus-C. Within 16 y of continuous commercial farming, Miscanthus stands accumulated a total of 17.7 Mg C ha1 derived from Miscanthus residues (C4-C), which is equivalent to 1.1 Mg C4-C ha1 y1. The annual surplus might function as CO2 credit within a greenhouse-gas balance. Moreover, the beneficial properties of Miscanthus cultivation combined with a low requirement on fertilization may justify the status of Miscanthus as a sustainable low-input bioenergy crop.
  • 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:
    • Mustafa, A.
    • Ellis, B.
    • Whalen, J.
    • Gul, S.
  • Source: Pedobiologia
  • Volume: 55
  • Issue: 6
  • Year: 2012
  • Summary: Alteration of plant lignin concentration is expected to affect the C mineralization of crop residues. Mutations of single genes involved in biosynthesis of secondary cell walls such as KNOTTED ARABIDOPSIS THALIANA 7 (KNAT7), PRODUCTION OF ANTHOCYANIN PIGMENT 1 (PAP1) also known as MYB75, and cinnamoyl CoA reductase 1 (CCR1) coding genes could change lignin concentration in specific plant tissues. This study assessed the CO2-C production of soil amended with stem and root tissues of down-regulated (k/o) and over expression (o/x) KNAT7 and MYB75 and the CCR1 k/o mutant lines of A. thaliana. KNAT7 k/o and MYB75 k/o were grown in two different environmental conditions (two cohorts) in the greenhouse. Oven dried, finely ground (<0.5 mm) stem and root residues underwent biochemical analysis, then were mixed separately with sandy loam or clay loam soil to assess CO2-C production under controlled laboratory conditions for 63 days. Compared to wild ecotypes, C:N ratio and acid unhydrolyzable fraction (AUF) concentration tended to be higher in stem residues of KNAT7 k/o and MYB75 k/o mutant lines. The C:N ratio was lower in stem and roots of CCR1 k/o line, and the AUF concentration was lower in CCR1 k/o stem residues than in the wild ecotypes. Hemicelluloses were lower in stem residues of KNAT7 k/o and MYB75 k/o (first cohort) than their wild ecotypes. Cumulative CO2-C production was lower in soil amended with stem residues of KNAT7 k/o (first cohort) and MYB75 k/o (first and second cohorts). CCR1 k/o stem tissues caused higher CO2-C production from soil. After 63 days incubation, the acid/aldehyde ratio (Ad/Al) of vanillin (V) and syringyl (S) lignin monomers of soil was higher for stem amended CCR1 k/o and lower for stem amended MYB75 k/o soils as compared to their wild ecotypes. Generally root residues caused lower CO2-C production from soil than stem residues. There was no difference in CO2-C production for root residues between mutant lines and their wild ecotypes. In conclusion, KNAT7 k/o, MYB75 k/o and CCR1 k/o mutations resulted in altered C:N ratio and resistant compounds (i.e., AUF) especially in stems, and these alterations in residue chemistry influenced CO2-C production and also lignin degradation in soil. (c) 2012 Elsevier GmbH. All rights reserved.
  • Authors:
    • Wenzel, H.
    • Olesen, J.
    • Petersen, B.
    • Jorgensen, U.
    • Hamelin, L.
  • Source: Global Change Biology Bioenergy
  • Volume: 4
  • Issue: 6
  • Year: 2012
  • Summary: This paper addresses the conversion of Danish agricultural land from food/feed crops to energy crops. To this end, a life cycle inventory, which relates the input and output flows from and to the environment of 528 different crop systems, is built and described. This includes seven crops (annuals and perennials), two soil types (sandy loam and sand), two climate types (wet and dry), three initial soil carbon level (high, average, low), two time horizons for soil carbon changes (20 and 100 years), two residues management practices (removal and incorporation into soil) as well as three soil carbon turnover rate reductions in response to the absence of tillage for some perennial crops (0%, 25%, 50%). For all crop systems, nutrient balances, balances between above- and below-ground residues, soil carbon changes, biogenic carbon dioxide flows, emissions of nitrogen compounds and losses of macro- and micronutrients are presented. The inventory results highlight Miscanthus as a promising energy crop, indicating it presents the lowest emissions of nitrogen compounds, the highest amount of carbon dioxide sequestrated from the atmosphere, a relatively high carbon turnover efficiency and allows to increase soil organic carbon. Results also show that the magnitude of these benefits depends on the harvest season, soil types and climatic conditions. Inventory results further highlight winter wheat as the only annual crop where straw removal for bioenergy may be sustainable, being the only annual crop not involving losses of soil organic carbon as a result of harvesting the straw. This, however, is conditional to manure application, and is only true on sandy soils.
  • Authors:
    • Ruiz R., R.
    • Henson, I.
    • Romero, H.
  • Source: Agronomia Colombiana
  • Volume: 30
  • Issue: 3
  • Year: 2012
  • Summary: Colombia is currently the world's fifth largest producer of palm oil and the largest producer in South and Central America. It has substantial areas of land that could be used for additional oil palm production and there is considerable scope for increasing yields of existing planted areas. Much of the vegetation on land suitable for conversion to oil palm has a low biomass, and so establishing oil palm plantations on such land should lead to an increase in carbon stock, thereby counteracting greenhouse gas (GHG) emissions responsible for global warming. The first part of this study examines changes in carbon stock in Colombia resulting from expansion of oil palm cultivation together with factors (offsets) that act to minimize carbon emissions. The results are subsequently used to construct a net GHG balance.
  • Authors:
    • Romero, H.
    • Ruiz R., R.
    • Henson, I.
  • Source: Agronomia Colombiana
  • Volume: 30
  • Issue: 3
  • Year: 2012
  • Summary: In the preceding paper we examined carbon sequestration in oil palm plantations and in mill products and by-products as part of a study of the greenhouse gas balance of palm oil production in Colombia, showing how this has changed over time. Here, we look at the opposing processes of greenhouse gas (GHG) emission and calculate the resulting net carbon budget for the industry. The main emission sources, in decreasing order of magnitude, assessed using "default" or "most probable" options, were found to be land use change (40.9% of total), mill methane production (21.4%), direct use of fossil fuel (18.5%), indirect use of fossil fuel (11.9%) and nitrous oxide production (7.3%). The total (gross) emissions, expressed in carbon equivalents (Ceq.), were less than the amount of sequestered carbon, resulting in a positive net Ceq. balance. All oil palm growing regions showed a net gain with the exception of the western zone, where emissions due to land-use change were judged to be substantial. Of the 11 alternative scenarios tested, only three resulted in Ceq. balances lower than the default and only two gave a negative balance.