Crop residues as raw materials for biorefinery systems – A LCA case study

Our strong dependence on fossil fuels results from the intensive use and consumption of petroleum derivatives which, combined with diminishing oil resources, causes environmental and political concerns. The utilization of agricultural residues as raw materials in a biorefinery is a promising alternative to fossil resources for production of energy carriers and chemicals, thus mitigating climate change and enhancing energy security. This paper focuses on a biorefinery concept which produces bioethanol, bioenergy and biochemicals from two types of agricultural residues, corn stover and wheat straw. These biorefinery systems are investigated using a Life Cycle Assessment (LCA) approach, which takes into account all the input and output flows occurring along the production chain. This approach can be applied to almost all the other patterns that convert lignocellulosic residues into bioenergy and biochemicals. The analysis elaborates on land use change aspects, i.e. the effects of crop residue removal (like decrease in grain yields, change in soil N₂O emissions and decrease of soil organic carbon). The biorefinery systems are compared with the respective fossil reference systems producing the same amount of products/services from fossils instead of biomass. Since climate change mitigation and energy security are the two most important driving forces for biorefinery development, the assessment focuses on greenhouse gas (GHG) emissions and cumulative primary energy demand, but other environmental categories are evaluated as well.Results show that the use of crop residues in a biorefinery saves GHG emissions and reduces fossil energy demand. For instance, GHG emissions are reduced by about 50% and more than 80% of non-renewable energy is saved. Land use change effects have a strong influence in the final GHG balance (about 50%), and their uncertainty is discussed in a sensitivity analysis. Concerning the investigation of the other impact categories, biorefinery systems have higher eutrophication potential than fossil reference systems. Based on these results, a residues-based biorefinery concept is able to solve two problems at the same time, namely find a use for the abundant lignocellulosic residues and ensure a mitigation effect for most of the environmental concerns related to the utilization of non-renewable energy resources.Therefore, when agricultural residues are used as feedstocks, best management practices and harvest rates need to be carefully established. In fact, rotation, tillage, fertilization management, soil properties and climate can play an important role in the determination of the amount of crop residue that can be removed minimizing soil carbon losses.     

The development of bioenergy technology in China

Among renewable energy resources, bioenergy is one of the fastest growth energy alternatives with tremendous potential in China. The thermal, physical, and biological processes of conversion of biomass yield a number of products and can be obtained as gases, liquids, solid fuels, and electricity as well as a variety of chemicals. Various bioenergy technologies that have been developed are at the fundamental research, demonstration, and commercialization stages. This review concentrates on the processes that are attracting the most attention in China.     

Spatial assessment of the bioenergy potential of forest residues in the western province of Spain, Caceres

The present work is mainly devoted to provide a rigorous analysis on the quantification, the mapping and the management of the bioenergy potential of forest residues from the most representative forestry species of the west-central region of Spain (Cáceres).An appropriate methodological approach for the estimate of potential biomass and potential bioenergy as well as the use of GIS for data process are both crucial for the design of thermal plants and for the accurate estimate of biomass collection and transportation costs, according to the scale economy of the plant.The total forest residues in the province of Cáceres are estimated as 463 000 t y⁻¹. The availability of such major biomass potential for energy production is strongly conditioned to the inherent difficulties during the extraction process. This way, an energy potential of 139 000 toe y⁻¹ would be achieved if the above-mentioned biomass collection rate is assumed.The method to optimise the search for suitable locations for thermal plants as well as for biomass extraction/collection areas, based on the combined use of GIS and spatial analysis techniques, is also described.     

Bioenergy transition in rural China: Policy options and co-benefits

This paper reviews the current situation of bioenergy development in China, particularly on its relationship to sustainable rural development. It argues that the current government strategy, investment policy and industrial interest are over-emphasized on biomass-burning power generation as part of the clean energy development trajectories, which may not lead to the most cost-effective outcomes in terms of investments, resource use and social development objectives. It points out that there are large potentials in developing and disseminating household-based biomass technologies in rural areas, especially with energy-efficient modern biomass stoves, which can produce far more economic, social and environmental benefits than biomass power plants. It is a decentralized solution to use renewable energy resources for meeting multi-objectives. It is suggested that key incentive policies be provided by the government to encourage this technological transition, or the leapfrogging from using traditional household stoves towards modern biomass stoves, which will lead to a win–win situation in global, regional and local environmental protection, sustainable resource management and related social benefits, particularly for the poor in remote communities. Six policy recommendations are made: (1) financial schemes development; (2) preferable tax and carbon tax; (3) regulatory policy reform; (4) service industry support; (5) market research, training and capacity building for key stakeholders; (6) development of methodologies and standards for CDM projects. The potential co-benefits brought up by this massive biomass technology transition will bring new perspectives to realizing Millennium Development Goals (MDGs) and global CO₂ emissions reduction targets in China, and also set an example to other developing countries.     

European wood pellet market integration - A study of the residential sector

The integration of European energy markets is a key goal of EU energy policy, and has also been the focal point of many scientific studies in recent years. International markets for coal, oil, natural gas and electricity have previously been investigated in order to determine the extent of the respective markets. This study enhances this field of research to bioenergy markets. Price series data and time series econometrics are used to determine whether residential sector wood pellet markets of Austria, Germany and Sweden are integrated. The results of the econometric tests show that the German and Austrian markets can be considered to be integrated, whereas the Swedish market is separate from the other two countries. Although increased internationalization of wood pellet markets is likely to contribute to European price convergence and market integration, this process is far from completed.     

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.     

Energy wood harvesting productivity of three harvesting methods in first thinning of scots pine (Pinus sylvestris L.)

Energy wood harvesting in young forests presents an economical challenge and has been dependent on subsidies in Finland. Whole-tree harvesting systems have proved to be most productive when carrying out energy wood harvesting in cleanings and early thinnings in young forests. The application of integrated energy wood and pulpwood harvesting is less common.It was hypothesized that multi-tree harvesting (MTH) with the OM-Waratah 745 single grip harvester head could change harvesting logistics and improve productivity for integrated energy wood and pulpwood thinnings. Two variations of MTH were compared with single-tree harvesting (STH). The logging methods studied were: (1) conventional single-tree harvesting with pulpwood and energy wood processed at the strip road; (2) multi-tree harvesting with pulpwood and energy wood processing along the strip road (MTH1); and (3) multi-tree harvesting at the stump where the aim was to leave the logging residues distributed evenly over the harvesting area and not on the strip roads (MTH2).MTH methods were 28-35% more productive than the single-tree harvesting. The biggest differences in work stages were found in the felling and delimbing stages. In single-tree harvesting felling was 9-26% and delimbing 14-27% slower than in multi-tree harvesting.MTH2 distributed 13% of residues further than 7 m from the strip road center. With STH and MTH1 only a good 1.2-1.7% was placed this far, and 74.4 and 62.0% respectively within 3 m.     

Bioenergy industries development in China: Dilemma and solution

Having 2.8 × 10⁸–3.0 × 10⁸ t/a of wood energy, 4.0 × 10⁶ t/a of oil seeds, 7.7 × 10⁸ t/a of crops straw, 3.97 × 10⁹ t/a of poultry and livestock manure, 1.48 × 10⁸ t/a of municipal waste, and 4.37 × 10¹⁰ t/a of organic wastewater, China is in possession of good resource condition for the development of bioenergy industries. Until the end of 2007, China has popularized 2.65 × 10⁷ rural household biogas, established 8318 large and middle-scale biogas projects, and produced 1.08 × 10¹⁰ m³/a of biogas; the production of bioethanol, biodiesel, biomass briquettes fuel and biomass power generation reached to 1.5 × 10⁶ t/a, 3.0 × 10⁵ t/a, 6.0 × 10⁴ t/a and 6.42 × 10⁹ kWh, respectively. In recent years, bioenergy industries developed increasingly fast in China. However, the industrial base was weak with some dilemma existing in raw material supply, technological capability, industry standards, policy and regulation, and follow-up services, etc. From the viewpoint of long-term effective development system for bioenergy industries in China, a series of policy suggestions have been offered, such as strengthening strategy research, improving bioenergy industries development policies and plan, enhancing scientific research input, persisting in technology innovation, establishing product quality standard, improving industrial standard system, opening market and accelerating commercialization, etc. It is expected that the advices mentioned above could be helpful for the improvement of bioenergy industries development.     

The impacts of energy prices on energy intensity: Evidence from China

In this paper, we present a review of the deregulation of energy prices in China between 1985 and 2004 and assess the impacts of changes in energy prices on aggregate energy intensity and coal/oil/electricity intensity. We used time series data to provide estimates of energy price elasticities. Empirical results showed that: (1) The own-price elasticities of coal, oil, and aggregate energy were negative in periods both before and after 1995, implying that higher relative prices of different energy types lead to the decrease in coal, oil, and aggregate energy intensities. However, the positive own-price elasticity of electricity after 1995 probably indicates that the price effect was weaker than other factors such as income effect and population effect. (2) The impacts of energy prices were asymmetric over time. (3) Sectoral adjustment also drove the decrease in aggregate energy intensity. Although raising energy prices to boost efficiency of energy use seems to be an effective policy tool, other policy implications concerned with energy prices, such as energy supply security and fuel poverty, must also be considered.     

Residential bioenergy heating: A study of consumer perceptions of improved woodstoves

Consumers’ choices play a key role for the development of biomass heating in the residential sector. The city of Oslo has granted subsidies to households who change to new, improved low-emission woodstoves. The purpose of this study is to expand the knowledge about users’ experiences and attitudes to residential biomass heating. An adapted model of the Theory of Planned Behavior was used to model households’ inclination to continue using their woodstoves for heating. More than 800 questionnaires were collected from households that recently had invested in an improved woodstove. The respondents were satisfied with the new woodstoves. The respondents also considered themselves competent to use and maintain the stove and few had problems acquiring fuelwood. Further analyses showed that the intention to continue to use the new woodstove depends on economic benefits, heating performance, perceived time and effort to operate the stove, environmental effects of heating as well as perceived subjective norm. The results imply that when marketing a modern technology for bioenergy heating, both public authorities and producers should consider issues related to the users’ perception of subjective norm, such as perceived status of using bioenergy or environmental concerns, when designing campaigns to promote the use of woodstoves.     

Bioethanol development in China and the potential impacts on its agricultural economy

China is now the third largest bioethanol producer in the world after the United State and Brazil. The overall goals of this paper are to provide an overview of China’s current bioethanol program, its future trend, and the likely impacts on its agricultural economy in the future. The analysis shows that China has developed an ambitious long-run biofuel program with a series of financial and institutional supports. While there are several potential feedstock crops available for bioethanol production, lack of land for feedstock production is one of major constraints in China’s bioethanol expansion. The results show that although China’s bioethanol expansion will have little impacts on overall agricultural prices in international markets, it will have significant impacts on the prices, productions, and trade of those energy crops being used for bioethanol production in China.     

Identification of potential areas for biomass production in China: Discussion of a recent approach and future challenges

A standard methodology is needed to recognize potentially suitable areas for sustainable bioenergy crop production. This facilitates better identification of promising crops and cropping systems, logistical and economic studies, and work needed to meet regulatory criteria. A possible approach is built upon three layers of internationally available spatial data: (1) degrading and abandoned areas, (2) potentially suitable land cover classes, (3) exclusion zones such as nature reserves and areas of high biodiversity. For China, areas identified as potentially suitable range from 1.2 to 6.0% of the national territory, depending on different levels of statistical confidence in degrading area status and allowable limits of terrestrial carbon. Verification on the ground showed that about 60% of points tested conformed to the remote suitability assessment in the scenario, which represents the results for the combination of all degrading areas and a terrestrial carbon stock limit of 200 t ha⁻¹. A top-down approach is useful in framing potentially suitable locations, but a complementary bottom-up analysis is still required to ultimately identify areas for sustainable bio-fuel production.