GCB Bioenergy
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Farmers' perspectives for the development of a bioenergy industry in <scp>I</scp>reland Abstract A survey of I rish farmers was conducted to identify farmers’ opinions on energy crop production and to characterize potential adopters of energy crop cultivation in I reland. One hundred and seventy‐two surveys were completed from 25 counties in I reland. M iscanthusI reland. The establishment of long‐term contracts and government schemes were identified as important requirements for the development of bioenergy crop production in I reland. Energy crop adoption was not limited to farmers undertaking specific farm enterprises. Farmers were motivated to adopt energy crop production for both economic and environmental benefits. These results are the first to provide valuable information on the perspectives of potential adopters of bioenergy crop production in Ireland for the promotion and implementation of a national bioenergy industry. Policy requirements and outreach strategies to encourage adoption of energy crops by agricultural producers are suggested.
GCB Bioenergy - Tập 4 Số 5 - Trang 597-610 - 2012
Multifaceted roles of duckweed in aquatic phytoremediation and bioproducts synthesis Abstract Duckweed (Lemnaceae) is a fast‐growing aquatic vascular plant. It has drawn an increasing attention worldwide due to its application in value‐added nutritional products and in sewage disposal. In particular, duckweed is a promising feedstock for bioenergy production. In this review, we summarized applications of duckweed from the following four aspects. Firstly, duckweed could utilize nitrogen, phosphorus, and inorganic nutrition in wastewater and reduces water eutrophication efficiently. During these processes, microorganisms play an important role in promoting duckweed growth and improving its tolerance to stresses. We also introduced our pilot‐scale test using duckweed for wastewater treatment and biomass production simultaneously. Secondly, its capability of fast accumulation of large amounts of starch makes duckweed a promising bioenergy feedstock, catering the currently increasing demand for bioethanol production. Pretreatment conditions prior to fermentation can be optimized to improve the conversion efficiency from starch to bioethanol. Furthermore, duckweed serves as an ideal source for food supply or animal feed because the composition of amino acids in duckweed is similar to that of whey protein, which is easily digested and assimilated by human and other animals. Finally, severing as a natural plant factory, duckweed has shown great potential in the production of pharmaceuticals and dietary supplements. With the surge of omics data and the development of Clustered Regularly Interspaced Short Palindromic Repeats technology, remodeling of the metabolic pathway in duckweed for synthetic biology study will be attainable in the future.
GCB Bioenergy - Tập 13 Số 1 - Trang 70-82 - 2021
Land‐use change to bioenergy production in <scp>E</scp>urope: implications for the greenhouse gas balance and soil carbon Abstract Bioenergy from crops is expected to make a considerable contribution to climate change mitigation. However, bioenergy is not necessarily carbon neutral because emissions of CO 2 , N2 O CH 4 during crop production may reduce or completely counterbalance CO 2 savings of the substituted fossil fuels. These greenhouse gases (GHG s) 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 E uropean bioenergy crops, although it focuses on dedicated perennial crops such as M iscanthus and short rotation coppice species. Such second‐generation crops account for only 3% of the current E uropean bioenergy production, but field data suggest they emit 40% to >99% less N2 O −1 yr−1 for poplar and willow and 0.66 Mg soil C ha−1 yr−1 for M iscanthus ). 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.
GCB Bioenergy - Tập 4 Số 4 - Trang 372-391 - 2012
Biochar stability in soil: meta‐analysis of decomposition and priming effects Abstract The stability and decomposition of biochar are fundamental to understand its persistence in soil, its contribution to carbon (C) sequestration, and thus its role in the global C cycle. Our current knowledge about the degradability of biochar, however, is limited. Using 128 observations of biochar‐derived CO 2 from 24 studies with stable (13 C) and radioactive (14 C) carbon isotopes, we meta‐analyzed the biochar decomposition in soil and estimated its mean residence time (MRT ). The decomposed amount of biochar increased logarithmically with experimental duration, and the decomposition rate decreased with time. The biochar decomposition rate varied significantly with experimental duration, feedstock, pyrolysis temperature, and soil clay content. The MRT s of labile and recalcitrant biochar C pools were estimated to be about 108 days and 556 years with pool sizes of 3% and 97%, respectively. These results show that only a small part of biochar is bioavailable and that the remaining 97% contribute directly to long‐term C sequestration in soil. The second database (116 observations from 21 studies) was used to evaluate the priming effects after biochar addition. Biochar slightly retarded the mineralization of soil organic matter (SOM ; overall mean: −3.8%, 95% CI = −8.1–0.8%) compared to the soil without biochar addition. Significant negative priming was common for studies with a duration shorter than half a year (−8.6%), crop‐derived biochar (−20.3%), fast pyrolysis (−18.9%), the lowest pyrolysis temperature (−18.5%), and small application amounts (−11.9%). In contrast, biochar addition to sandy soils strongly stimulated SOM mineralization by 20.8%. This indicates that biochar stimulates microbial activities especially in soils with low fertility. Furthermore, abiotic and biotic processes, as well as the characteristics of biochar and soils, affecting biochar decomposition are discussed. We conclude that biochar can persist in soils on a centennial scale and that it has a positive effect on SOM dynamics and thus on C sequestration.
GCB Bioenergy - Tập 8 Số 3 - Trang 512-523 - 2016
Effects of biochar application on soil greenhouse gas fluxes: a meta‐analysis Abstract Biochar application to soils may increase carbon (C) sequestration due to the inputs of recalcitrant organic C. However, the effects of biochar application on the soil greenhouse gas (GHG ) fluxes appear variable among many case studies; therefore, the efficacy of biochar as a carbon sequestration agent for climate change mitigation remains uncertain. We performed a meta‐analysis of 91 published papers with 552 paired comparisons to obtain a central tendency of three main GHG fluxes (i.e., CO 2 , CH 4 , and N2 O) in response to biochar application. Our results showed that biochar application significantly increased soil CO 2 fluxes by 22.14%, but decreased N2 O fluxes by 30.92% and did not affect CH 4 fluxes. As a consequence, biochar application may significantly contribute to an increased global warming potential (GWP ) of total soil GHG fluxes due to the large stimulation of CO 2 fluxes. However, soil CO 2 fluxes were suppressed when biochar was added to fertilized soils, indicating that biochar application is unlikely to stimulate CO 2 fluxes in the agriculture sector, in which N fertilizer inputs are common. Responses of soil GHG fluxes mainly varied with biochar feedstock source and soil texture and the pyrolysis temperature of biochar. Soil and biochar pH , biochar applied rate, and latitude also influence soil GHG fluxes, but to a more limited extent. Our findings provide a scientific basis for developing more rational strategies toward widespread adoption of biochar as a soil amendment for climate change mitigation.
GCB Bioenergy - Tập 9 Số 4 - Trang 743-755 - 2017
The effect of pyrolysis conditions on biochar stability as determined by three methods Abstract Biochar is the porous, carbonaceous material produced by thermochemical treatment of organic materials in an oxygen‐limited environment. In general, most biochar can be considered resistant to chemical and biological decomposition, and therefore suitable for carbon (C) sequestration. However, to assess the C sequestration potential of different types of biochar, a reliable determination of their stability is needed. Several techniques for assessing biochar stability have been proposed, e.g. proximate analysis, oxygen (O): C ratio and hydrogen (H): C ratio; however, none of them are yet widely recognized nor validated for this purpose. Biochar produced from three feedstocks (Pine, Rice husk and Wheat straw) at four temperatures (350, 450, 550 and 650 °C) and two heating rates (5 and 100 °C min−1 ) was analysed using three methods of stability determination: proximate analysis, ultimate analysis and a new analytical tool developed at the UK Biochar Research Centre known as the Edinburgh accelerated ageing tool (Edinburgh stability tool). As expected, increased pyrolysis temperatures resulted in higher fractions of stable C and total C due to an increased release of volatiles. Data from the Edinburgh stability tool were compared with those obtained by the other methods, i.e. fixed C, volatile matter, O : C and H : C ratios, to investigate potential relationships between them. Results of this comparison showed that there was a strong correlation (R > 0.79) between the stable C determined by the Edinburgh stability tool and fixed C, volatile matter and O : C, however, H : C showed a weaker correlation (R = 0.65). An understanding of the influence of feedstock and production conditions on the long‐term stability of biochar is pivotal for its function as a C mitigation measure, as production and use of unstable biochar would result in a relatively rapid return of C into the atmosphere, thus potentially intensifying climate change rather than alleviating it.
GCB Bioenergy - Tập 5 Số 2 - Trang 122-131 - 2013
Aged biochar affects gross nitrogen mineralization and recovery: a <sup>15</sup>N study in two contrasting soils Abstract Biochar is a pyrolysed biomass and largely consists of pyrogenic carbon (C), which takes much longer to decompose compared to the biomass it is made from. When applied to soil, it could increase agricultural productivity through nutrient retention and changing soil properties. The biochar‐mediated nutrient retention capacity depends on the biochar properties, which change with time, and on soil properties. Here, we examined the effects of a wood biochar (20 t ha−1 ), that has aged (21 months) in a grassland field, on gross nitrogen (N) mineralization (GNM ) and 15 N recovery using a 15 N tracer. A field experiment was conducted in two soil types, that is a Tenosol and a Dermosol, and also included a phosphorus (P) addition treatment (1 kg ha−1 ). Compared to the control, biochar with P addition significantly increased GNM in the Tenosol. Possibly, biochar and P addition enhanced nutrient availability in this nutrient‐limited soil, thereby stimulating microbial activity. In contrast, biochar addition reduced GNM in the Dermosol, possibly by protecting soil organic matter (SOM ) from decomposition through sorption onto biochar surfaces and enhanced formation of organo‐mineral complexes in this soil that had a higher clay content (29% vs. 8% in the Tenosol). Compared to the control, biochar significantly increased total 15 N recovery in the Tenosol (on average by 12%) and reduced leaching to subsurface soil layers (on average by 52%). Overall, 15 N recovery was greater in the Dermosol (83%) than the Tenosol (63%), but was not affected by biochar or P. The increased N recovery with biochar addition in the sandy Tenosol may be due to
GCB Bioenergy - Tập 9 Số 7 - Trang 1196-1206 - 2017
Identifying potential areas for biofuel production and evaluating the environmental effects: a case study of the<scp>J</scp>ames<scp>R</scp>iver<scp>B</scp>asin in the<scp>M</scp>idwestern<scp>U</scp>nited<scp>S</scp>tates Abstract Biofuels are now an important resource in theU nitedS tates because of theE nergyI ndependence andS ecurityA ct of 2007. Both increased corn growth for ethanol production and perennial dedicated energy crop growth for cellulosic feedstocks are potential sources to meet the rising demand for biofuels. However, these measures may cause adverse environmental consequences that are not yet fully understood. This study 1) evaluates the long‐term impacts of increased frequency of corn in the crop rotation system on water quantity and quality as well as soil fertility in theJ amesR iverB asin and 2) identifies potential grasslands for cultivating bioenergy crops (e.g. switchgrass), estimating the water quality impacts. We selected the soil and water assessment tool, a physically based multidisciplinary model, as the modeling approach to simulate a series of biofuel production scenarios involving crop rotation and land cover changes. The model simulations with different crop rotation scenarios indicate that decreases in water yield and soil nitrate nitrogen (NO 3 ‐N ) concentration along with an increase inNO 3 ‐N load to stream water could justify serious concerns regarding increased corn rotations in this basin. Simulations with land cover change scenarios helped us spatially classify the grasslands in terms of biomass productivity and nitrogen loads, and we further derived the relationship of biomass production targets and the resulting nitrogen loads against switchgrass planting acreages. The suggested economically efficient (planting acreage) and environmentally friendly (water quality) planting locations and acreages can be a valuable guide for cultivating switchgrass in this basin. This information, along with the projected environmental costs (i.e. reduced water yield and increased nitrogen load), can contribute to decision support tools for land managers to seek the sustainability of biofuel development in this region.
GCB Bioenergy - Tập 4 Số 6 - Trang 875-888 - 2012
Biochar amendment of soil improves resilience to climate change Abstract Because of climate change, insufficient soil moisture may increasingly limit crop productivity in certain regions of the world. This may be particularly consequential for biofuel crops, many of which will likely be grown in drought‐prone soils to avoid competition with food crops. Biochar is the byproduct of a biofuel production method called pyrolysis. If pyrolysis becomes more common as some scientists predict, biochar will become more widely available. We asked, therefore, whether the addition of biochar to soils could significantly increase the availability of water to a crop. Biochar made from switchgrass (Panicum virgatum L.) shoots was added at the rate of 1% of dry weight to four soils of varying texture, and available water contents were calculated as the difference between field capacity and permanent wilting point water contents. Biochar addition significantly increased the available water contents of the soils by both increasing the amount of water held at field capacity and allowing plants to draw the soil to a lower water content before wilting. Among the four soils tested, biochar amendment resulted in an additional 0.8–2.7 d of transpiration, which could increase productivity in drought‐prone regions or reduce the frequency of irrigation. Biochar amendment of soils may thus be a viable means of mitigating some of the predicted decrease in water availability accompanying climate change that could limit the future productivity of biofuel crops.
GCB Bioenergy - Tập 7 Số 5 - Trang 1084-1091 - 2015
Trade‐offs between land and water requirements for large‐scale bioenergy production Abstract Bioenergy is expected to play an important role in the future energy mix as it can substitute fossil fuels and contribute to climate change mitigation. However, large‐scale bioenergy cultivation may put substantial pressure on land and water resources. While irrigated bioenergy production can reduce the pressure on land due to higher yields, associated irrigation water requirements may lead to degradation of freshwater ecosystems and to conflicts with other potential users. In this article, we investigate the trade‐offs between land and water requirements of large‐scale bioenergy production. To this end, we adopt an exogenous demand trajectory for bioenergy from dedicated energy crops, targeted at limiting greenhouse gas emissions in the energy sector to 1100 Gt carbon dioxide equivalent until 2095. We then use the spatially explicit global land‐ and water‐use allocation model MA gPIE to project the implications of this bioenergy target for global land and water resources. We find that producing 300 EJ yr−1 of bioenergy in 2095 from dedicated bioenergy crops is likely to double agricultural water withdrawals if no explicit water protection policies are implemented. Since current human water withdrawals are dominated by agriculture and already lead to ecosystem degradation and biodiversity loss, such a doubling will pose a severe threat to freshwater ecosystems. If irrigated bioenergy production is prohibited to prevent negative impacts of bioenergy cultivation on water resources, bioenergy land requirements for meeting a 300 EJ yr−1 bioenergy target increase substantially (+ 41%) – mainly at the expense of pasture areas and tropical forests. Thus, avoiding negative environmental impacts of large‐scale bioenergy production will require policies that balance associated water and land requirements.
GCB Bioenergy - Tập 8 Số 1 - Trang 11-24 - 2016
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