Life cycle assessment of a Brassica carinata bioenergy cropping system in southern Europe

The energetic and environmental performance of production and distribution of the Brassica carinata biomass crop in Soria (Spain) is analysed using life cycle assessment (LCA) methodology in order to demonstrate the major potential that the crop has in southern Europe as a lignocellulosic fuel for use as a renewable energy source.The Life Cycle Impact Assessment (LCIA) including midpoint impact analysis that was performed shows that the use of fertilizers is the action with the highest impact in six of the 10 environmental categories considered, representing between 51% and 68% of the impact in these categories.The second most important impact is produced when the diesel is used in tractors and transport vehicles which represents between 48% and 77%. The contribution of the B. carinata cropping system to the global warming category is 12.7 g CO₂ eq. MJ⁻¹ biomass produced. Assuming a preliminary estimation of the B. carinata capacity of translocated CO₂ (631 kg CO₂ ha⁻¹) from below-ground biomass into the soil, the emissions are reduced by up to 5.2 g CO₂ eq. MJ⁻¹.The production and transport are as far as a thermoelectric plant of the B. carinata biomass used as a solid fuel consumes 0.12 MJ of primary energy per 1 MJ of biomass energy stored. In comparison with other fossil fuels such as natural gas, it reduces primary energy consumption by 33.2% and greenhouse gas emission from 33.1% to 71.2% depending on whether the capacity of translocated CO₂ is considered or not.The results of the analysis support the assertion that B. carinata crops are viable from an energy balance and environmental perspective for producing lignocellulosic solid fuel destined for the production of energy in southern Europe. Furthermore, the performance of the crop could be improved, thus increasing the energy and environmental benefits.     

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.     

Forest treatment residues for thermal energy compared with disposal by onsite burning: Emissions and energy return

Mill residues from forest industries are the source for most of the current wood-based energy in the US, approximately 2.1% of the nation's energy use in 2007. Forest residues from silvicultural treatments, which include limbs, tops, and small non-commercial trees removed for various forest management objectives, represent an additional source of woody biomass for energy. We spatially analyzed collecting, grinding, and hauling forest residue biomass on a 515,900 ha area in western Montana, US, to compare the total emissions of burning forest residues in a boiler for thermal energy with the alternatives of onsite disposal by pile-burning and using either natural gas or #2 distillate oil to produce the equivalent amount of useable energy. When compared to the pile-burn/fossil fuel alternatives, carbon dioxide emissions from the bioenergy alternative were approximately 60%, methane emissions were approximately 3%, and particulate emissions less than 10 μm were 11% and 41%, respectively, for emission control and no-control boilers. Emissions from diesel consumption for collecting, grinding, and hauling biomass represented less than 5% of the total bioenergy emissions at an average haul distance of 136 km. Across the study area, an average 21 units of bioenergy were produced for each unit of diesel energy used to collect, grind, and haul biomass. Fossil fuel energy saved by the bioenergy alternative relative to the pile-burn/fossil fuel alternatives averaged 14.7–15.2 GJ t^?1 of biomass.     

Feasibility assessment of poplar bioenergy systems in the Southern Europe

A detailed reliability assessment of bioenergy production systems based on poplar cultivation was made. The aim of this assessment was to demonstrate the Economic feasibility of implementing poplar biomass production for power generation in Spain. The assessment considers the following chain of energy generation: cultivation and harvesting, and transportation and electricity generation in biomass power plants (10, 25 and 50 MW). Twelve scenarios were analysed in accordance with the following: two harvesting methods (high density packed stems and chip production in the field), two crop distributions around the power plant and three power plant sizes. The results show that the cost of biomass delivered at power plant ranges from 18.65 to 23.96 € Mg^?1 dry basis. According to power plant size, net profits range from 3 to 22 million € per yr.Sensibility analyses applied to capital cost at the power plant and to biomass production in the field demonstrate that they do not affect the feasibility of these systems. Reliability is improved if benefits through selling CO₂ emission credits are taken into account.This study clears up the Economic uncertainty of poplar biomass energy systems that already has been accepted as environmentally friendlier and as offering better energetic performance.     

A comparative analysis of woody biomass and coal for electricity generation under various CO2 emission reductions and taxes

Mitigating global climate change via CO₂ emission control and taxation is likely to enhance the economic potential of bioenergy production and utilization. This study investigated the cost competitiveness of woody biomass for electricity production in the US under alternative CO₂ emission reductions and taxes. We first simulated changes in the price of coal for electricity production due to CO₂ emission reductions and taxation using a computable general equilibrium model. Then, the costs of electricity generation fueled by energy crops (hybrid poplar), logging residues, and coal were estimated using the capital budgeting method. Our results indicate that logging residues would be competitive with coal if emissions were taxed at about US$25 Mg⁻¹ CO₂, while an emission tax US$100 Mg⁻¹ CO₂ or higher would be needed for hybrid poplar plantations at a yield of 11.21 dry Mg ha⁻¹ yr⁻¹ (5 dry tons ac⁻¹ yr⁻¹) to compete with coal in electricity production. Reaching the CO₂ emission targets committed under the Kyoto Protocol would only slightly increase the price of fossil fuels, generating little impact on the competitiveness of woody biomass. However, the price of coal used for electricity production would significantly increase if global CO₂ emissions were curtailed by 20% or more. Logging residues would become a competitive fuel source for electricity production if current global CO₂ emissions were cut by 20–30%. Hybrid poplar plantations would not be able to compete with coal until emissions were reduced by 40% or more.     

Worldwide commercial development of bioenergy with a focus on energy crop-based projects

Bioenergy consumption is greatest in countries with heavy subsidies or tax incentives, such as China, Brazil, and Sweden. Conversion of forest residues and agricultural residues to charcoal, district heat and home heating are the most common forms of bioenergy. Biomass electric generation feedstocks are predominantly forest residues (including black liquor), bagasse, and other agricultural residues. Biofuel feedstocks include sugar from sugarcane (in Brazil), starch from maize grain (in the US), and oil seeds (soy or rapeseed) for biodiesel (in the US, EU, and Brazil). Of the six large land areas of the world reviewed (China, EU, US, Brazil, Canada, Australia), total biomass energy consumptions amounts to 17.1 EJ. Short-rotation woody crops (SRWC) established in Brazil, New Zealand, and Australia over the past 25 years equal about 50,000 km². SRWC plantings in China may be in the range of 70,000–100,000 km². SRWC and other energy crops established in the US and EU amount to less than 1000 km². With some exceptions (most notably in Sweden and Brazil), the SRWC have been established for purposes other than as dedicated bioenergy feedstocks, however, portions of the crops are (or are planned to be) used for bioenergy production. New renewable energy incentives, greenhouse gas emission targets, synergism with industrial waste management projects, and oil prices exceeding 60 $ Bbl⁻¹ (in 2005) are major drivers for SRWC or energy crop based bioenergy projects.     

Understanding energy systems change in Canada: 1. Decomposition of total energy intensity

Between 1995 and 2010, the total energy intensity (E/GDP, PJ/Gross Domestic Product in 2002$) of the Canadian economy declined by 23% or − 2.64 MJ/$. To understand why, the Logarithmic Mean Divisia Index (LMD-I) method was used to decompose a large body of government statistical data supporting the observed E/GDP decline. The analysis shows that (a) 48% (1.27 MJ/$) of the decline was associated with an inter-sector structural change in the economy (i.e. an increased contribution to the total GDP of the low energy-using commercial and institutional sector compared with the high energy-using manufacturing and heavy industry sectors); (b) 24% (0.62 MJ/$) was attributed to the impact of the Canadian GDP growing faster than population; (c) 22% (0.58 MJ/$) of the decline was associated with an overall decrease in business energy intensity. A deeper analysis of business sectors shows a positive impact of 0.4 MJ/$ from increased energy intensity in the oil and gas sector, offset by a 0.98 MJ/$ decline due to energy intensity declines in the other business sectors; (d) 6.3% (0.17 MJ/$) of the decline was associated with an improvement in the energy intensity of households, mostly from residential energy use rather than personal transportation energy use. These results provide insights for policy makers regarding those aspects of the Canadian economy that contribute to, or work against, efforts to transform energy systems toward sustainability.     

Large-scale bioenergy production from soybeans and switchgrass in Argentina: Part B. Environmental and socio-economic impacts on a regional level

The feasibility of deploying a socio-economic and environmental impact analysis for large-scale bioenergy production on a regional level is analyzed, based on a set of defined criteria and indicators. The analysis is done for La Pampa province in Argentina. The case study results in conclusions in how far the criteria can be verified ex ante based on available methodologies and data sources. The impacts are analyzed for two bioenergy chains (soybeans and switchgrass) for a set of defined land use scenarios. The carbon stock change for switchgrass ranges from 0.2 to 1.2 ton C/ha/year and for soybean from ?1.2 to 0 ton C/ha/year, depending on the scenario. The GHG emission reduction ranges from 88% to 133% for the switchgrass bioenergy chain (replacing coal or natural gas) and from 16% to 94% for the soybean bioenergy chain (replacing fossil fuel) for various lifetime periods. The annual soil loss, compared to the reference land use system is 2–10 ton/ha for the soybean bioenergy chain and 1–2 ton/ha for the switchgrass bioenergy chain. In total, nine sustainability principles are analyzed. In the case of switchgrass, most environmental benefits can be achieved when produced on suitable land of abandoned cropland. Soybean production for bioenergy shows a good overall sustainability performance if produced on abandoned cropland. The production of switchgrass on degraded grassland shows socio-economic and environmental benefits, which is not the case for soybean production. The production of bioenergy production on non-degraded grassland is not preferred. It is concluded that the scenario approach enables understanding of the complexity of the bioenergy chain and the underlying factors influencing the sustainability principles. It is difficult to give ex ante a final conclusion whether a bioenergy chain is sustainable or not as this depends not only on the previous land use system but also on other factors as the selection of the bioenergy crop, the suitable agroecological zone and the agricultural management system applied. The results also imply that it is possible to steer for a large part the sustainability performance of a bioenergy chain during project development and implementation. Land use planning plays a key role in this process.     

The economical and environmental performance of miscanthus and switchgrass production and supply chains in a European setting

The purpose of this study is to analyse the economical and environmental performance of switchgrass and miscanthus production and supply chains in the European Union (EU25), for the years 2004 and 2030. The environmental performance refers to the greenhouse gas (GHG) emissions, the primary fossil energy use and to the impact on fresh water reserves, soil erosion and biodiversity. Analyses are carried out for regions in five countries. The lowest costs of producing (including storing and transporting across 100 km) in the year 2004 are calculated for Poland, Hungary and Lithuania at 43–64 € per oven dry tonne (odt) or 2.4–3.6 € GJ^?1 higher heating value. This cost level is roughly equivalent to the price of natural gas (3.1 € GJ^?1) and lower than the price of crude oil (4.6 € GJ^?1) in 2004, but higher than the price of coal (1.7 € GJ^?1) in 2004. The costs of biomass in Italy and the United Kingdom are somewhat higher (65–105 € odt^?1 or 3.6–5.8 € GJ^?1). The doubling of the price of crude oil and natural gas that is projected for the period 2004–2030, combined with nearly stable biomass production costs, makes the production of perennial grasses competitive with natural gas and fossil oil. The results also show that the substitution of fossil fuels by biomass from perennial grasses is a robust strategy to reduce fossil energy use and curb GHG emissions, provided that perennial grasses are grown on agricultural land (cropland or pastures). However, in such case deep percolation and runoff of water are reduced, which can lead to overexploitation of fresh water reservoirs. This can be avoided by selecting suitable locations (away from direct accessible fresh water reservoirs) and by limiting the size of the plantations. The impacts on biodiversity are generally favourable compared to conventional crops, but the location of the plantation compared to other vegetation types and the size and harvesting regime of the plantation are important variables.     

Distribution and potential of bioenergy resources from agricultural activities in Mexico

Biomass is the most abundant and versatile form of renewable energy in the world. The bioenergy production from crop residues is compatible with both food and energy production. Currently, several technologies are available for transforming crop residues into utilizable energy such as direct combustion and fermentation. Mexico is the third largest country in LAC in terms of the cropland area and would become a central focus of attention for the production of biofuels. In this paper we examined the type, location and quantities of various crop residues in Mexico to evaluate their potential for conversion into bioenergy through combustion and fermentation. It was estimated that 75.73 million tons of dry matter was generated from 20 crops in Mexico. From this biomass, 60.13 million tons corresponds to primary crop residues mainly from corn straw, sorghum straw, tops/leaves of sugarcane and wheat straw. The generation of secondary crop residues accounted for 15.60 million tons to which sugarcane bagasse, corncobs, maguey bagasse and coffee pulp were the main contributors. The distribution of this biomass showed that several Mexican municipalities had very high by-product potentials where each municipality could have an installed capacity of 78 MW (via direct combustion) or 0.3 million m³ of bioethanol per year (via anaerobic fermentation). The identification of these municipalities where the biomass potential is high is important since it constitutes the first step towards evaluating the current biomass availability and accurately estimating the bioenergy production capacity from crop residues.     

An evaluation of greenhouse gas mitigation options for coal-fired power plants in the US Great Lakes States

We assessed options for mitigating greenhouse gas emissions from electricity generation in the US Great Lakes States, a region heavily dependent on coal-fired power plants. A proposed 600 MW power plant in northern Lower Michigan, USA provided context for our evaluation. Options to offset fossil CO₂ emissions by 20% included biomass fuel substitution from (1) forest residuals, (2) short-rotation woody crops, or (3) switchgrass; (4) biologic sequestration in forest plantations; and (5) geologic sequestration using CO₂ capture. Review of timber product output data, land cover data, and expected energy crop productivity on idle agriculture land within 120 km of the plant revealed that biomass from forestry residuals has the potential to offset 6% and from energy crops 27% of the annual fossil fuel requirement. Furthermore, annual forest harvest in the region is only 26% of growth and the surplus represents a large opportunity for forest products and bioenergy applications. We used Life Cycle Assessment (LCA) to compare mitigation options, using fossil energy demand and greenhouse gas emissions per unit electricity generation as criteria. LCA results revealed that co-firing with forestry residuals is the most attractive option and geologic sequestration is the least attractive option, based on the two criteria. Biologic sequestration is intermediate but likely infeasible because of very large land area requirements. Our study revealed that biomass feedstock potentials from land and forest resources are not limiting mitigation activities, but the most practical approach is likely a combination of options that optimize additional social, environmental and economic criteria.     

Comparison of Arundo donax L. and Miscanthus x giganteus in a long-term field experiment in Central Italy: Analysis of productive characteristics and energy balance

Miscanthus x giganteus (miscanthus) and Arundo donax L. (giant reed) are two perennial crops which have been received particular attention during the last decade as bioenergy crops. The main aim of the present study was to compare the above-ground biomass production and the energy balance of these perennial rhizomatous grasses in a long-term field experiment. The crops were cultivated from 1992 to 2003 in the temperate climate of Central Italy with 20,000 plants ha^?1, 100–100–100 kg N, P₂O₅, K₂O per hectare, and without irrigation supply. For each year of trial, biomass was harvested in autumn to estimate biometric characteristics and productive parameters. Besides, energy analysis of biomass production was carried out determining energy output, energy input, energy efficiency (output/input) and net energy yield (output–input). Results showed high above-ground biomass yields over a period of 10 years for both species, with better productive performances in giant reed than in miscanthus (37.7 t DM ha^?1 year^?1 vs 28.7 t DM ha^?1 year^?1 averaged from 2 to 12 years of growth). Such high yields resulted positively correlated to number of stalks (miscanthus), plant height and stalk diameter (giant reed). Moreover, these perennial species are characterised by a favourable energy balance with a net energy yield of 467 and 637 GJ ha^?1 (1–12 year mean) for miscanthus and giant reed respectively.With such characteristics, both grasses could be proposed as biomass energy crops in Southern Europe with a significant and environmentally compatible contribution to energy needs.     

The impact of sustainability criteria on the costs and potentials of bioenergy production – Applied for case studies in Brazil and Ukraine

The goal of this paper is to analyse the impact of the implementation of a certification system on the management system (costs) of and the availability of land (quantity) for bioenergy production. Twelve socio-economic areas of concern (food supply, child labour, (minimum) wages, employment, health care and education) and environmental areas of concern (soil erosion, depletion of fresh water resources, nutrient losses and soil nutrient depletion, pollution from chemicals and biodiversity) are included. Since there is no generally accepted definition of sustainability, a loose and strict set of criteria are defined. Short rotation coppice (SRC) production systems in Ukraine and South East Brazil in 2015 are taken as case studies. The results indicate that it seems feasible to produce biomass for energy purposes at reasonable cost levels and meeting strict sustainability criteria at the same time. The loose set of criteria has no impact on the costs of energy crop production, which are calculated to be 1.7 € GJ^?1 in Brazil and 2.1 € GJ^?1 in Ukraine. The strict set of criteria results in an increase of the costs of energy crop production by 42 % in Brazil and 14 % in Ukraine. In general, compliance with strict socio-economic criteria has a limited impact on the costs, because SRC is relatively labour extensive. Strict environmental criteria likely have a larger impact.     

Effect of biomass species and plant size on cellulosic ethanol: A comparative process and economic analysis

The effects of five different biomass species and their chemical composition on the overall process efficiency and economic performance considering feedstock availability and feedstock costs to manufacture ethanol from lignocellulose were studied. First is a comparison of ethanol production and excess electricity generated between different biomass species. Results show that, at the same feedstock rate of 2000 Mg day^?1, aspen wood has larger ethanol production than switchgrass, hybrid poplar and corn stover, while the excess electricity generated is as follows in increasing order: aspen < corn stover < hybrid poplar/switchgrass. Second, our results show that the ethanol production is largely linear with holocellulose (cellulose plus hemicellulose) composition of the various biomass species. However, the relationship between excess electricity generated and non-holocellulose combustible component is nonlinear. Last, on environmental performance, it is found that the water losses per unit ethanol production are in the following order: aspen wood < corn stover < hybrid poplar < switchgrass. While corn stover is a potential feedstock to produce cellulosic ethanol with the lowest ethanol production cost at the present time, hybrid poplar and switchgrass are the two promising future energy crops.The effects of plant size analysis showed that the estimated feedstock delivered costs, ethanol production, excess electricity generated and solid and gaseous waste emissions all increase with plant size for the various biomass species. The ethanol production costs decrease with the increase in plant size with optimal plant sizes for corn stover in the range from 2000 dry Mg day^?1 to 4000 dry Mg day^?1.     

Optimization of bioenergy yield from cultivated land in Denmark

A cost minimization model for supply of starch, oil, sugar, grassy and woody biomass for bioenergy in Denmark was developed using linear programming. The model includes biomass supply from annual crops on arable land, short rotation forestry (willow) and plantation forestry. Crop area distributions were simulated using cost data for year 2005. Five scenarios with different constraints, e.g. on food and feed supply and on nitrogen balance were considered focusing on: a) constraints as the year 2005, b) landscape aesthetics and biodiversity c) groundwater protection, d) maintaining current food and feed production, or e) on site carbon sequestration. In addition, two oil price levels were considered. The crop area distributions differed between scenarios and were affected by changing fossil oil prices up to index 300 (using 55$ per barrel in 2005 as index = 100). The bioenergy supply (district heating, electric power, biogas, RME or bioethanol) varied between 56 PJ in the “2005” scenario at oil index 100 and 158 PJ at oil index 300 in the groundwater scenario. Our simple model demonstrates the effect of prioritizing multiple uses of land resources for food, feed or bioenergy, while maintaining a low nitrogen load to the environment. In conclusion, even after drastic landuse changes the bioenergy supply as final energy will not exceed 184 PJ annually (including 26 PJ processed biowaste sources) by far lower than the annual domestic total energy consumption ranging between 800 and 850 PJ yr^?1.     

Life-cycle assessment of electricity from biomass: Case studies of two biocrops in Spain

Through the Renewable Energies Plan 2000–2010, Spain has fixed the objective of covering 12% of the primary energy demand from renewable sources. The achievement of this objective implies an annual increase of 22.4% of the energy produced from renewable sources. In this context, the objective of this study is to determine if the electricity from biomass produced in Spain would be environmentally competitive with electricity from natural gas or from the Spanish electricity mix. For that, the environmental impacts associated to the whole life cycle of two energetic crops in Spain, Poplar and Ethiopian mustard, used for power generation were evaluated. The overall assessment includes the cultivation and collection of biomass, its transport and the processes of its energetic transformation. We calculated different scenarios of electricity production from biomass in different capacity power plants (10, 25 or 50 MW), different transport scenarios and different productivities for biomass production. Our results show that, given the assumptions of this study, Ethiopian mustard is more impacting than Poplar when used for electricity production. Also, the transportation of biomass from the field to the power plant is an important stage that has to be carefully planned in order to get the maximum amount of electricity with a minimum environmental impact. Compared to electricity from natural gas or the Spanish electricity mix, the electricity obtained from biomass is more impacting in three from six impact categories we present here.     

Biogas generation potential by anaerobic digestion for sustainable energy development in India

The potential of biogas generation from anaerobic digestion of different waste biomass in India has been studied. Renewable energy from biomass is one of the most efficient and effective options among the various other alternative sources of energy currently available. The anaerobic digestion of biomass requires less capital investment and per unit production cost as compared to other renewable energy sources such as hydro, solar and wind. Further, renewable energy from biomass is available as a domestic resource in the rural areas, which is not subject to world price fluctuations or the supply uncertainties as of imported and conventional fuels. In India, energy demand from various sectors is increased substantially and the energy supply is not in pace with the demand which resulted in a deficit of 11,436 MW which is equivalent to 12.6% of peak demand in 2006. The total installed capacity of bioenergy generation till 2007 from solid biomass and waste to energy is about 1227 MW against a potential of 25,700 MW. The bioenergy potential from municipal solid waste, crop residue and agricultural waste, wastewater sludge, animal manure, industrial waste which includes distilleries, dairy plants, pulp and paper, poultry, slaughter houses, sugar industries is estimated. The total potential of biogas from all the above sources excluding wastewater has been estimated to be 40,734 Mm³/year.     

Productive use of bioenergy for rural household in ecological fragile area,Panam County,Tibet in China: The case of the residential biogas model

Bioenergy is the major domestic energy for rural households in developing countries due to its cheap or easy-getting characteristics. Productive use of bioenergy is an important strategy for rural households to improve not only their income, but also their health, living environment and so on. In Tibet of China, which is rich in cattle dung and firewood as the major energy sources for rural households, the efficiency of energy utilization is just about 10%. In order to improve energy utilization efficiency and the living conditions for rural residents, the Tibet Autonomous Region government introduced residential biogas model (RBM) to local households, which was a comprehensive utilization system of energy integrated with residential biogas digester, vegetable greenhouse and livestock shed. This paper aims to show the productive use of the bioenergy by the RBM, which could be depicted as the feasibility and the benefits on economic, eco-environmental and social aspects of biogas utilization, based on household questionnaires in Panam County. In RBM, biogas digester works as the biomass material supplement loop to transform originally biomass flow from single-direction to recycling-direction. The results indicate that the output of unit biogas digester could replace 1.44 t of firewood, 1.65 t of agricultural residues and 1.75 t of cattle dung, respectively. The net incremental benefit of RBM could reach 5550.72 Yuan in 15 years. The reduced amount of CO₂ emission when substituted by biogas in other agricultural areas and the areas of semi-agricultural and semi-husbandry in Tibet could be (76.66–79.89) × 10⁴ t/year and the capability for nitrogen storage could achieve (0.39–0.99) × 10⁴ t/year. The amount of cattle dung replaced by biogas could reach 78.29 × 10⁴ t/year; this means that the saved cattle dung, 3.51 t/hm², could be reallocated back to cultivated land to improve the soil fertility and to keep the balance of nutrient elements in cultivated land. Biogas utilization reduces the labor opportunity costs of women compared to use of traditional bioenergy sources. It could be concluded that the productive use of bioenergy through RBM in this area has its capability to release the current pressures on biomass sources by adjusting patterns of rural energy consumption, and to improve the conditions of health, environment, economy and energy conservation.     

Quantitative appraisal and potential analysis for primary biomass resources for energy utilization in China

As the largest agricultural country, China has abundant biomass resources, but the distribution is scattered and difficult to collect. It is essential to estimate the biomass resource and its potential for bioenergy utilization in China. In this study, the amount of main biomass resources for possible energy use and their energy utilization potential in China are analyzed based on statistical data. The results showed that the biomass resource for possible energy use amounted to 8.87 × 10⁸ tce in 2007 of which the crops straw is 1.42 × 10⁸ tce, the forest biomass is 2.85 × 10⁸ tce, the poultry and livestock manure is 4.40 × 10⁷ tce, the municipal solid waste is 1.35 × 10⁶ tce, and the organic waste water is 6.46 × 10⁶ tce. Through the information by thematic map, it is indicated that, except arctic-alpine areas and deserts, the biomass resource for possible energy use was presented a relatively average distribution in China, but large gap was existed in different regions in the concentration of biomass resources, with the characteristics of East dense and West sparse. It is indicated that the energy transformation efficiency of biomass compressing and shaping, biomass anaerobic fermentation and biomass gasification for heating have higher conversion efficiency. If all of the biomass resources for possible energy use are utilized by these three forms respectively, 7.66 × 10¹² t of biomass briquettes fuel, 1.98 × 10¹² m³ of low calorific value gas and 3.84 × 10¹¹ m³ of biogas could be produced, 3.65 × 10⁸ t to 4.90 × 10⁸ t of coal consumption could be substituted, and 6.12 × 10⁸ t to 7.53 × 10⁸ t of CO₂ emissions could be reduced. With the enormous energy utilization potential of biomass resources and the prominent benefit of energy saving and emission reduction, it proves an effective way to adjust the energy consumption structure, to alleviate the energy crisis, to ensure the national energy security and to mitigate the global warming trend.     

Short-rotation forestry of birch,maple, poplar and willow in Flanders (Belgium) II. Energy production and CO2 emission reduction potential

Belgium, being an EU country, has committed itself to a 7.5% reduction of greenhouse gas emissions during the first commitment period of the Kyoto Protocol. Within this framework, the Flemish government aims at reaching a share of 6% of renewable electricity in the total electricity production by 2010. In this work, the biomass production of birch, maple, poplar and willow in a short-rotation forestry (SRF) plantation after a 4-year growth period served as the base to calculate the amount of (electrical) energy that could be produced by this type of bioenergy crop in Flanders. The maximum amount of electricity that could be provided by SRF biomass was estimated at 72.9 GWh_e year⁻¹, which only accounts for 0.16% of the total electricity production in this region. Although the energy output was rather low, the bioenergy production process under consideration appeared to be more energy efficient than energy production processes based on fossil fuels. The high efficiency of birch compared to the other species was mainly due to the high calorific value of the birch wood. The maximum CO₂ emission reduction potential of SRF plantations in Flanders was estimated at only 0.09% of the total annual CO₂ emission. The most interesting application of SRF in Flanders seemed to be the establishment of small-scale plantations, linked to a local combined heat and power plant. These plantations could be established on marginal arable soils or on polluted sites, and they could be of importance in the densely populated area of Flanders because of other environmental benefits, among which their function as (temporary) habitat for many species.