Net N2O and CH4 soil fluxes of annual and perennial bioenergy crops in two central German regions

The area used for bioenergy feedstock production is increasing because substitution of fossil fuels by bioenergy is promoted as an option to reduce greenhouse gas (GHG) emissions. However, agriculture itself contributes to rising atmospheric nitrous oxide (N₂O) and methane (CH₄) concentrations. In this study we tested whether the net exchanges of N₂O and CH₄ between soil and atmosphere differ between annual fertilized and perennial unfertilized bioenergy crops. We measured N₂O and CH₄ soil fluxes from poplar short rotation coppice (SRC), perennial grass-clover and annual bioenergy crops (silage maize, oilseed rape, winter wheat) in two central German regions for two years. In the second year after establishment, the N₂O emissions were significantly lower in SRC (<0.1 kg N₂O–N ha⁻¹ yr⁻¹) than grassland (0.8 kg N₂O–N ha⁻¹ yr⁻¹) and the annual crop (winter wheat; 1.5 kg N₂O–N ha⁻¹ yr⁻¹) at one regional site (Reiffenhausen). However, a different trend was observed in the first year when contents of mineral nitrogen were still higher in SRC due to former cropland use. At the other regional site (Gierstädt), N₂O emissions were generally low (<0.5 kg N₂O–N ha⁻¹ yr⁻¹) and no crop-type effects were detected. Net uptake of atmospheric CH₄ varied between 0.4 and 1.2 kg CH₄–C ha⁻¹ yr⁻¹ with no consistent crop-type effect. The N₂O emissions related to gross energy in the harvested biomass ranged from 0.07 to 6.22 kg CO₂ equ GJ⁻¹. In both regions, Gierstädt (low N₂O emissions) and more distinct Reiffenhausen (medium N₂O emissions), this energy yield-related N₂O emission was the lowest for SRC.     

Coupling of energy and agricultural policies on promoting the production of biomass energy from energy crops and grasses in Taiwan

This paper examined promotion programs and implementing regulations that provide a framework for the application of energy and agricultural policies for the local energy crops cultivation by the reactivation of fallow land (about 100,000 ha) and their utilizations in the bioenergy production in Taiwan. The contents were thus addressed on current energy supply and biomass energy production, estimation of carbon dioxide (CO₂) emissions from energy use (consumption) using the Reference Approach of the Intergovernmental Panel on Climate Change (IPCC) method, national energy goal in biomass energy supply in the near future, and government policies and measures for encouraging bioenergy production and consumption. For the promotion of biofuels, the incentive programs were initiated in the period of 2006–2011. The potential benefits of the program include the upgrade of industrial investment in the bioenergy plants, the reactivation of fallow land (about 100,000 ha), the mitigation of CO₂ emissions, and so on. Concerning the utilization of napier grass (a potential energy grass) as biomass energy (electricity generation) for co-firing, its impacts on ambient air quality and non-CO₂ greenhouse gases (i.e., CH₄ and N₂O) emissions were also discussed in the paper.     

Executive Summary

This study reviewed the literature on corn and cellulosic ethanol for their potential to replace petroleum fuels. Metrics include: energy yield, cropland requirements, and pollution reduction. The key findings are that an agreement exists among the literature that corn production yields are insufficient to warrant large-scale production. The required cropland is far in excess of the available corn cropland. Furthermore, the use of corn for ethanol fuel will lead to continued increases in food prices worldwide. When these findings are considered along with the marginal improvement in CO₂ emissions and other pollutants, it is apparent that corn ethanol is not viable for replacing petroleum fuels. In contrast, this study found that cellulosic ethanol, which can be grown on marginal cropland, provides a much greater energy yield and a significantly greater pollution reduction. In summary, cellulosic ethanol could provide one alternative to petroleum fuels and is deserving of large-scale test experimentation to conclusively demonstrate viability.     

A conceptual framework for estimating the climate impacts of land-use change due to energy crop programs

In this paper I discuss general conceptual issues in the estimation of the impacts of CO₂ emissions from soils and biomass, over time, as a result of land-use change (LUC) due to increased demand for energy crops. The effect of LUC on climate depends generally on the magnitude and timing of changes in soil and plant carbon, and in particular on the timing and extent of the reversion of land to original ecosystems at the end of the bioenergy program. Depending on whether one counts the climate impacts of any reversion of land uses, and how one values future climate-change impacts relative to present impacts, one can estimate anywhere from zero to very large climate impacts due to land-use change (LUC). I argue that the best method is to estimate the net present value (NPV) of the impacts of climate change due to LUC. With this approach, one counts the reversion impacts at the end of the program and applies a continuous discounting function to future impacts to express them in present terms. In this case, the impacts of CO₂ emissions from the initial LUC then are at least partially offset by the impacts of CO₂ sequestration from reversion.     

GHG balances of bioenergy systems – Overview of key steps in the production chain and methodological concerns

This paper deals with a methodology for calculating the greenhouse gas (GHG) balances of bioenergy systems producing electricity, heat and transportation biofuels from biomass residues or crops. Proceeding from the standard Life-Cycle Assessment (LCA) as defined by ISO 14040 norms, this work provides an overview of the application of the LCA methodology to bioenergy systems in order to estimate GHG balances. In this paper, key steps in the bioenergy chain are identified and the bioenergy systems are compared with fossil reference systems producing the same amount of final products/services. The GHG emission balances of the two systems can thus be compared. Afterwards, the most important methodological assumptions (e.g. functional unit, allocation, reference system, system boundaries) and key aspects affecting the final outcomes are discussed. These key aspects are: changes in organic carbon pools, land-use change effects (both direct and indirect), N₂O and CH₄ emissions from agricultural soils and effects of crop residue removal for bioenergy use. This paper finally provides some guidelines concerning the compilation of GHG balances of bioenergy systems, with recommendations and indications on how to show final results, address the key methodological issues and give homogenous findings (in order to enhance the comparison across case studies).     

Life cycle GHG emissions from Malaysian oil palm bioenergy development: The impact on transportation sector's energy security

Malaysia's transportation sector accounts for 41% of the country's total energy use. The country is expected to become a net oil importer by the year 2011. To encourage renewable energy development and relieve the country's emerging oil dependence, in 2006 the government mandated blending 5% palm-oil biodiesel in petroleum diesel. Malaysia produced 16 million tonnes of palm oil in 2007, mainly for food use. This paper addresses maximizing bioenergy use from oil-palm to support Malaysia's energy initiative while minimizing greenhouse-gas emissions from land-use change. When converting primary and secondary forests to oil-palm plantations between 270–530 and 120–190 g CO₂-equivalent per MJ of biodiesel produced, respectively, is released. However, converting degraded lands results in the capture of between 23 and 85 g CO₂-equivalent per MJ of biodiesel produced. Using various combinations of land types, Malaysia could meet the 5% biodiesel target with a net GHG savings of about 1.03 million tonnes (4.9% of the transportation sector's diesel emissions) when accounting for the emissions savings from the diesel fuel displaced. These findings are used to recommend policies for mitigating GHG emissions impacts from the growth of palm oil use in the transportation sector.     

Historical carbon budget of the brazilian ethanol program

This work models the carbon neutralization capacity of Brazil's ethanol program since 1975. In addition to biofuel, we also assessed the mitigation potential of other energy products, such as, bioelectricity, and CO₂ emissions captured during fermentation of sugar cane's juice. Finally, we projected the neutralization capacity of sugar cane's bio-energy system over the next 32 years. The balance between several carbon stocks and flows was considered in the model, including the effects of land-use change. Our results show that the neutralization of the carbon released due to land-use change was attained only in 1992, and the maximum mitigation potential of the sugar cane sector was 128 tonnes of CO₂ per ha in 2006. An ideal reconstitution of the deployment of the sugar cane sector, including the full exploitation of bio-electricity's potential, plus the capture of CO₂ released during fermentation, shows that the neutralization of land-use change emissions would have been achieved in 1988, and its mitigation potential would have been 390 tCO₂/ha. Finally, forecasts of the sector up to 2039 shows that the mitigation potential in 2039 corresponds to 836 tCO₂/ha, which corresponds to 5.51 kg of CO₂ per liter of ethanol produced, or 55% above the negative emission level.     

Life cycle assessment of different bioenergy production systems including perennial and annual crops

Energy crops are expected to greatly develop in a very short-term bringing to significant social and environmental benefits. Nevertheless, a significant number of studies report from very positive to negative environmental implications from growing and processing energy crops, thus great uncertainty still remains on this argument. The present study focused on the cradle-to-grave impact assessments of alternative scenarios including annual and perennial energy crops for electricity/heat or first and second generation transport fuels, giving special emphasis to agricultural practices which are frequently surprisingly neglected in Life Cycle Assessment studies despite a not secondary relevance on final outcomes. The results show that cradle-to-farm gate impacts, i.e. including the upstream processes, may account for up to 95% of total impacts, with dominant effects on marine water ecotoxicity. Therefore, by increasing the sustainability of crop management through minimizing agronomic inputs, or with a complementary use of crop resides, can be expected to significantly improve the overall sustainability of bioenergy chains, as well as the competitiveness against fossil counterparts. Once again, perennial crops resulted in substantially higher environmental benefits than annual crops. It is shown that significant amount of emitted CO₂ can be avoided through converting arable lands into perennial grasslands. Besides, due to lack of certain data, soil carbon storage was not included in the calculations, while N₂O emission was considered as omitted variable bias (1% of N-fertilization). Therefore, especially for perennial grasses, CO₂ savings were reasonably higher that those estimated in the present study. For first generation biodiesel, sunflower showed a lower energy-based impacts than rapeseed, while wheat should be preferred over maize for first generation bioethanol given its lower land-based impacts. For second generation biofuels and thermo-chemical energy, switchgrass provided the highest environmental benefits. With regard to bioenergy systems, first generation biodiesel was less impacting than first generation bioethanol; bioelectricity was less impacting than first generation biofuels and second generation bioethanol by thermo-chemical hydrolysis, but highly impacting than Biomass-to-Liquid biodiesel and second generation bioethanol through enzymatic hydrolysis.     

Bioenergy overview for Portugal

Bioenergy is seen as one of the key options to mitigate greenhouse gas emissions and substitute fossil fuels. Bioenergy is also an atypical energy source due to its diversity and inter-linkages with many other technological and policy areas. The goal of this paper is to analyze the Portuguese possibilities for bioenergy provision from biomass. The potentials of biomass, conversion technologies and legal framework are analysed and discussed. The result of this analysis shows that there are still unused potentials especially from forestry, which can contribute significantly to cover the bioenergy targets. However, the Portuguese experience with conversion technologies is limited to combustion, which is a drawback that must be solved so as to the bioenergy potential can be used. Research and Development projects, as well as demonstration projects are needed in order to improve the efficiency of the technological processes. At political level, Portuguese governments have been following the policies and strategies of the European Commission in the energy sector. However, energy crops market, due to the inter-linkage with agricultural policy, seems to need some additional political push.     

Multiple calibration decomposition analysis: Energy use and carbon dioxide emissions in the Japanese economy, 1970–1995

The purpose of this paper is to present a new approach to evaluating structural change of the economy in a multisector general equilibrium framework. The multiple calibration technique is applied to an ex post decomposition analysis of structural change between periods, enabling the distinction between price substitution and technological change to be made for each sector. This approach has the advantage of sounder microtheoretical underpinnings when compared with conventional decomposition methods. The proposed technique is empirically applied to changes in energy use and carbon dioxide (CO₂) emissions in the Japanese economy from 1970 to 1995. The results show that technological change is of great importance for curtailing energy use and CO₂ emissions in Japan. Total CO₂ emissions increased during this period primarily because of economic growth, which is represented by final demand effects. On the other hand, the effects such as technological change for labor or energy mitigated the increase in CO₂ emissions.     

Economic and greenhouse gas emission analysis of bioenergy production using multi-product crops—case studies for the Netherlands and Poland

In the face of climate change that may result from greenhouse gas (GHG) emissions, the scarcity of agricultural land and limited competitiveness of biomass energy on the market, it is desirable to increase the performance of bioenergy systems. Multi-product crops, i.e. using a crop partially for energy and partially for material purposes can possibly create additional incomes as well as additional GHG emission reductions. In this study, the performance of several multi-product crop systems is compared to energy crop systems, focused on the costs of primary biomass fuel costs and GHG emission reductions per hectare of biomass production. The sensitivity of the results is studied by means of a Monte-Carlo analysis. The multi-product crops studied are wheat, hemp and poplar in the Netherlands and Poland. GHG emission reductions of these multi-product crop systems are found to be between 0.2 and 2.4 Mg CO_2eq/(ha yr) in Poland and 0.9 and 7.8 Mg CO_2eq/(ha yr) in the Netherlands, while primary biomass fuel costs range from −4.1 to −1.7 €/GJ in the Netherlands and from 0.1 to 9.8 €/GJ in Poland. Results show that the economic attractiveness of multi-product crops depends strongly on material market prices, crop production costs and crop yields. Net annual GHG emission reductions per hectare are influenced strongly by the specific GHG emission reduction of material use, reference energy systems and GHG emissions of crop production. Multi-product use of crops can significantly decrease primary biomass fuel costs. However, this does not apply in general, but depends on the kind of crops and material uses. For the examples analysed here, net annual GHG emission reductions per hectare are not lowered by multi-product use of crops. Consequently, multi-product crops are not for granted an option to increase the performance of bioenergy systems. Further research on the feasibility of large-scale multi-product crop systems and their impact on land and material markets is desirable.     

Carbon dioxide emissions from switchgrass and cottonwood grown as bioenergy crops in the Lower Mississippi River Alluvial Valley

Marginal land of the Lower Mississippi Alluvial Valley (LMAV) has the potential to be utilized for substantial production of bioenergy feedstocks. However, resulting ecosystem services associated with dedicated bioenergy crop production, such as soil respiration and carbon dioxide (CO₂) emissions, which play an important role in global carbon (C) cycling, are not well understood. The objective of this study was to evaluate the effects of land use [i.e., switchgrass (Panicum virgatum) and eastern cottonwood (Populus deltoides) grown as dedicated bioenergy crops and a soybean (Glycine max)-grain sorghum (Sorghum bicolor) agroecosystem rotation] on monthly respiration and estimated annual CO₂ emissions for 2012 and 2013 from a silt -loam soil in east-central Arkansas. Peak monthly fluxes achieved each year differed (p < 0.05) somewhat among ecosystems. Annual CO₂ emissions differed among ecosystems (p < 0.001), but not between years (p = 0.45). Cottonwood emitted less CO₂ in both years (7.3 and 7.4 Mg ha⁻¹ for 2012 and 2013, respectively) compared to the other two ecosystems, while emissions from the switchgrass did not differ from those from the soybean in 2012 (10.3 and 9.5 Mg ha⁻¹, respectively) or grain sorghum in 2013 (9.7 and 9.2 Mg ha⁻¹, respectively). Results showed established bioenergy feedstock cropping systems do not have greater soil CO₂ emissions compared with a traditional soybean-grain sorghum crop rotation. Results also indicated that different bioenergy feedstocks can produce different quantities of CO₂ emissions, which may be important to consider when converting marginal lands to bioenergy feedstock cropping systems.     

Bioenergy driven land use change impacts on soil greenhouse gas regulation under Short Rotation Forestry

Second-generation bioenergy crops, including Short Rotation Forestry (SRF), have the potential to contribute to greenhouse gas (GHG) emissions savings through reduced soil GHG fluxes and greater soil C sequestration. If we are to predict the magnitude of any such GHG benefits a better understanding is needed of the effect of land use change (LUC) on the underlying factors which regulate GHG fluxes. Under controlled conditions we measured soil GHG flux potentials, and associated soil physico-chemical and microbial community characteristics for a range of LUC transitions from grassland land uses to SRF. These involved ten broadleaved and seven coniferous transitions. Differences in GHGs and microbial community composition assessed by phospholipid fatty acids (PLFA) profiles were detected between land uses, with distinctions between broadleaved and coniferous tree species. Compared to grassland controls, CO₂ flux, total PLFAs and fungal PLFAs (on a mass of C basis), were lower under coniferous species but unaffected under broadleaved tree species. There were no significant differences in N₂O and CH₄ flux rates between grassland, broadleaved and coniferous land uses, though both CH₄ and N₂O tended to have greater uptake under broadleaved species in the upper soil layer. Effect sizes of CO₂ flux across LUC transitions were positively related with effect sizes of soil pH, total PLFA and fungal PLFA. These relationships between fluxes and microbial community suggest that LUC to SRF may drive change in soil respiration by altering the composition of the soil microbial community. These findings support that LUC to SRF for bioenergy can contribute towards C savings and GHG mitigation.     

Fuel ethanol from cane molasses in Thailand: Environmental and cost performance

In the context of the world's energy crisis and environmental concerns, crop-based ethanol has emerged as an energy alternative, the use of which can help reduce oil imports as well as emissions of CO₂ and other air pollutants. However, a clear disadvantage of ethanol is its high cost over gasoline under the current pricing scheme that does not include externalities. The intent of this study is to perform a life cycle analysis comparing environmental and cost performance of molasses-based E10 with those of CG. The results show that although E10 provides reduction in fossil energy use, petroleum use, CO₂ and NO_x emissions, its total social costs are higher than those of gasoline due to higher direct production costs and external costs for other air emissions, e.g. CH₄, N₂O, CO, SO₂, VOC and PM₁₀. An analysis of projection scenarios shows that technological innovations towards cleaner production help maximize ethanol's benefits whilst minimizing its limitations.     

An energy balance and greenhouse gas profile for county Wexford,Ireland in 2006

In this paper an energy balance and a greenhouse gas profile has been formulated for the county of Wexford, situated in the south east of Ireland. The energy balance aims to aggregate all energy consumption in the county for the year 2006 across the following sectors; residential, agriculture, commerce and industry, and transport. The results of the energy balance are compared with the previous energy balance of 2001 where it is found that the residential sector is the biggest emitter of CO₂ with 38% of total emissions with the transport and industry/commerce sectors sharing second place on 28%. Consumption of oil is seen to have increased significantly in nearly all sectors, accounting for over 70% of the total final energy consumed (TFC) while the total primary energy requirement (TPER) sees oil consumption accounting for 91% of all fuels consumed. To take into account the contribution of agriculture in total GHG emissions the gases CH₄ and N₂O will be estimated from the agricultural and waste sectors. The results show that methane contributes 25% of total GHG emissions with agriculture being the primary contributor accounting for 36% of total emissions.     

Nitrogen fertilization of switchgrass increases biomass yield and improves net greenhouse gas balance in northern Michigan, U.S.A

Nitrogen (N) fertilization can increase bioenergy crop production; however, fertilizer production and application can contribute to greenhouse gas (GHG) emissions, potentially undermining the GHG benefits of bioenergy crops. The objective of this study was to evaluate the effects of N fertilization on GHG emissions and biomass production of switchgrass bioenergy crop, in northern Michigan. Nitrogen fertilization treatments included 0 kg ha⁻¹ (control), 56 kg ha⁻¹ (low) and 112 kg ha⁻¹ (high) of N applied as urea. Soil fluxes of CO₂, N₂O and CH₄ were measured every two weeks using static chambers. Indirect GHG emissions associated with field activities, manufacturing and transport of fertilizer and pesticides were derived from the literature. Switchgrass aboveground biomass yield was evaluated at the end of the growing season. Nitrogen fertilization contributed little to soil GHG emissions; relative to the control, there were additional global warming potential of 0.7 Mg ha⁻¹ y⁻¹ and 1.5 Mg ha⁻¹ y⁻¹ as CO₂ equivalents (CO₂eq), calculated using the IPCC values, in the low and high N fertilization treatments, respectively. However, N fertilization greatly stimulated CO₂ uptake by switchgrass, resulting in 1.5- and 2.5-fold increases in biomass yield in the low and high N fertilization treatments, respectively. Nitrogen amendments improved the net GHG benefits by 2.6 Mg ha⁻¹ y⁻¹ and 9.4 Mg ha⁻¹ y⁻¹ as CO₂eq relative to the control. Results suggest that N fertilization of switchgrass in this region could reduce (15-50%) the land base needed for bioenergy production and decrease pressure on land for food and forage crop production.     

Cost-effective CO2 emission reduction through heat,power and biofuel production from woody biomass: A spatially explicit comparison of conversion technologies

Bioenergy is regarded as cost-effective option to reduce CO₂ emissions from fossil fuel combustion. Among newly developed biomass conversion technologies are biomass integrated gas combined cycle plants (BIGCC) as well as ethanol and methanol production based on woody biomass feedstock. Furthermore, bioenergy systems with carbon capture and storage (BECS) may allow negative CO₂ emissions in the future. It is still not clear which woody biomass conversion technology reduces fossil CO₂ emissions at least costs. This article presents a spatial explicit optimization model that assesses new biomass conversion technologies for fuel, heat and power production and compares them with woody pellets for heat production in Austria. The spatial distributions of biomass supply and energy demand have significant impact on the total supply costs of alternative bioenergy systems and are therefore included in the modeling process. Many model parameters that describe new bioenergy technologies are uncertain, because some of the technologies are not commercially developed yet. Monte-Carlo simulations are used to analyze model parameter uncertainty. Model results show that heat production with pellets is to be preferred over BIGCC at low carbon prices while BECS is cost-effective to reduce CO₂ emissions at higher carbon prices. Fuel production – methanol as well as ethanol – reduces less CO₂ emissions and is therefore less cost-effective in reducing CO₂ emissions.     

A comparative study of bioenergy consumption and CO2 emissions in Tibetan region of China

Bioenergy is an important energy source for Tibetans. To compensate for the lack of a comparative study on household bioenergy consumption and CO₂ emissions among farming region, farming-pastoral region, pastoral region, and forest edge zones in Tibetan area, the authors conducted the comparative study through field investigation, literature review and data analysis. The study results reveal that: (1)Bioenergy consumption show regularity from high to low in forest edge zones, pastoral region, farming-pastoral region and farming region, respectively, but the CO₂ emissions change from high to low in forest edge zones, pastoral region, farming region, and farming-pastoral region, respectively in Tibetan area; (2)Remote geographic locations and traditional nomadic system restricts Tibetan pastoral region from use of diversified energy, resulting in higher bioenergy consumption and CO₂ emissions; (3)The energy efficiency could be potentially increased by improving energy structures and by using durable, low cost and easy to carry clean energy facilities.     

A projection for global CO2 emissions from the industrial sector through 2030 based on activity level and technology changes

In this study, we simulate global CO₂ emissions and their reduction potentials in the industrial sector up to the year 2030. Future industrial CO₂ emissions depend on changes in both technology and industrial activity. However, earlier bottom-up analyses mainly focused on technology change. In this study, we estimate changes in both technology and industrial activity. We developed a three-part simulation system. The first part is a macro economic model that simulates macro economic indicators, such as GDP and value added by sector. The second part consists of industrial production models that simulate future steel and cement production. The third part is a bottom-up type technology model that estimates future CO₂ emissions. Assuming no changes in technology since 2005, we estimate that global CO₂ emissions in 2030 increase by 15 GtCO₂ from 2005 level. This increase is due to growth in industrial production. Introducing technological reduction options within 100 US$/tCO₂ provides a reduction potential of 5.3 GtCO₂ compared to the case of no technology changes. As a result, even with large technological reduction potential, global industrial CO₂ emissions in 2030 are estimated to be higher as compared to 2005 level because of growth of industrial production.     

China's transportation energy consumption and CO2 emissions from a global perspective

Rapidly growing energy demand from China's transportation sector in the last two decades have raised concerns over national energy security, local air pollution, and carbon dioxide (CO₂) emissions, and there is broad consensus that China's transportation sector will continue to grow in the coming decades. This paper explores the future development of China's transportation sector in terms of service demands, final energy consumption, and CO₂ emissions, and their interactions with global climate policy. This study develops a detailed China transportation energy model that is nested in an integrated assessment model—Global Change Assessment Model (GCAM)—to evaluate the long-term energy consumption and CO₂ emissions of China's transportation sector from a global perspective. The analysis suggests that, without major policy intervention, future transportation energy consumption and CO₂ emissions will continue to rapidly increase and the transportation sector will remain heavily reliant on fossil fuels. Although carbon price policies may significantly reduce the sector's energy consumption and CO₂ emissions, the associated changes in service demands and modal split will be modest, particularly in the passenger transport sector. The analysis also suggests that it is more difficult to decarbonize the transportation sector than other sectors of the economy, primarily owing to its heavy reliance on petroleum products.