The trade-off between bioenergy and emissions with land constraints

Agricultural biofuels require the use of scarce land, and this land has opportunity cost. We explore the objective function of a social planner who includes a land constraint in the optimization decision to minimize environmental cost. The inclusion of this land constraint in our optimization model motivates the measurement of emissions on a per-hectare basis. Switchgrass and corn are modeled as competing alternatives to show how the inclusion of a land constraint can influence life cycle rankings and alter policy conclusions. With land use unconstrained, ethanol produced from switchgrass is always an optimal feedstock relative to ethanol produced from corn. With land use constrained, however, our results show that it is unlikely that switchgrass would be optimal in the midwestern United States, but may be optimal in southern states if carbon is priced relatively high. Whether biofuel policy advocates for one feedstock over another should consider these contrasting results.     

Global bioenergy potentials from agricultural land in 2050: Sensitivity to climate change, diets and yields

There is a growing recognition that the interrelations between agriculture, food, bioenergy, and climate change have to be better understood in order to derive more realistic estimates of future bioenergy potentials. This article estimates global bioenergy potentials in the year 2050, following a "food first" approach. It presents integrated food, livestock, agriculture, and bioenergy scenarios for the year 2050 based on a consistent representation of FAO projections of future agricultural development in a global biomass balance model. The model discerns 11 regions, 10 crop aggregates, 2 livestock aggregates, and 10 food aggregates. It incorporates detailed accounts of land use, global net primary production (NPP) and its human appropriation as well as socioeconomic biomass flow balances for the year 2000 that are modified according to a set of scenario assumptions to derive the biomass potential for 2050. We calculate the amount of biomass required to feed humans and livestock, considering losses between biomass supply and provision of final products. Based on this biomass balance as well as on global land-use data, we evaluate the potential to grow bioenergy crops and estimate the residue potentials from cropland (forestry is outside the scope of this study). We assess the sensitivity of the biomass potential to assumptions on diets, agricultural yields, cropland expansion and climate change. We use the dynamic global vegetation model LPJmL to evaluate possible impacts of changes in temperature, precipitation, and elevated CO(2) on agricultural yields. We find that the gross (primary) bioenergy potential ranges from 64 to 161?EJ?y(-1), depending on climate impact, yields and diet, while the dependency on cropland expansion is weak. We conclude that food requirements for a growing world population, in particular feed required for livestock, strongly influence bioenergy potentials, and that integrated approaches are needed to optimize food and bioenergy supply.     

The impact of oil prices on bioenergy,emissions and land use

We evaluate how alternative future oil prices will influence the penetration of biofuels, energy production, greenhouse gas (GHG) emissions, land use and other outcomes. Our analysis employs a global economy wide model and simulates alternative oil prices out to 2050 with and without a price on GHG emissions. In one case considered, based on estimates of available resources, technological progress and energy demand, the reference oil price rises to $124 by 2050. Other cases separately consider constant reference oil prices of $50, $75 and $100, which are targeted by adjusting the quantity of oil resources. In our simulations, higher oil prices lead to more biofuel production, more land being used for bioenergy crops, and fewer GHG emissions. Reducing oil resources to simulate higher oil prices has a strong income effect, so decreased food demand under higher oil prices results in an increase in land allocated to natural forests. We also find that introducing a carbon price reduces the differences in oil use and GHG emissions across oil price cases.     

Cropping bioenergy and biomaterials in marginal land: The added value of the biorefinery concept

A biorefinery is an integrated pattern of farming and conversion activities capable to provide bioenergy and biomaterials as alternative to fossil-based refineries, increasing jobs and income in rural areas. Considering the need to avoid competition with food production in arable land, non-food cropping on marginal land is being explored worldwide focusing on lignocellulosic crops (“second-generation” substrates). The viability of bioenergy and biochemicals from non-food crops in marginal land of Southern Italy was explored, using Brassica carinata as a test crop. An LCA-consistent, integrated evaluation method, named SUMMA (Sustainability multi-scale multi-method Approach) was applied for joint assessment of material, embodied energy, environmental support (emergy) and economic flows and performance. Two hypotheses were tested: (a) cropping for bioenergy (biodiesel + heat); (b) bioenergy and biomaterials within a biorefinery framework. In addition to biodiesel production from seeds, the first hypothesis assumes the conversion of residues (cake meal and straw) into heat for local industrial use, while the second one is based on a lignocellulose-to-chemicals biorefinery. Cropping for bioenergy provides a small net energy yield with no economic return. Instead, converting lignocellulosic residues to high added value biochemicals definitely improves the process performance from both energetic and economic points of view.     

Factors affecting forestland owners' allocation of non-forested land to pine plantation for bioenergy in Virginia

Studies have shown that woody bioenergy can have potential economic, social, and environmental benefits. One of the ways to meet the growing biomass demand for woody bioenergy is by allocating currently non-forested land for growing feedstocks such as pine. Towards this end, we conducted a survey on 900 randomly selected private forestland owners in Virginia and asked what proportion of their non-forested land they would allocate for loblolly pine at given bid prices. We then used recursive partitioning based Tobit regression to analyze data. Our results suggest that the experience of having supplied wood for chip-n-saw mills in the past five years, large land holding, prior experience with state/federal financial/technical support programs, among other factors, lead to smaller proportion of non-forested land being allocated for pine. However, a higher price offer, stronger preference for producing non-timber forest products such as evergreen boughs and grapevine, and lesser dependence on working the land for annual income lead to larger proportion of non-forested land being allocate for pine. Our results could assist policy makers in developing and improving land use and energy policies, certification programs, and extension and outreach services. Our contribution also includes the use of threshold analyses to delineate tipping points in variables associated with different response rates and showing the different effect of variables in terms of how they affect the supply of biomass and the supply of land for bioenergy purposes.     

Carbon sequestration potential of forest land: Management for products and bioenergy versus preservation

A 40 year projection of potential carbon sequestration is based on USDA Forest Service Forest Inventory and Analysis (FIA) data from the state of Georgia. The objective is to compare carbon sequestration under a sustainable management strategy versus a preservation strategy. FIA plots are projected ahead in time with hotdeck matching. This matches each subject plot with another plot from the database that represents the subject plot at a future time. The matched plot sequences are used to provide input data to a harvest scheduling program to generate a management strategy for the state. The sequestration from the management strategy is compared with a preservation strategy that involves no harvesting. Harvested wood is assumed to go into products with various half life decay rates. Carbon sequestration is increased as increasing proportions go into wood for energy, which is treated like a product with an infinite half life. Therefore, the harvested carbon does not return immediately to the atmosphere. Public land and land close to cities is assumed to be unavailable, and all other private land is assumed to be accessible. The results are presented as gigatonnes of CO₂ equivalent to make them directly comparable to US annual carbon emissions. The conclusion is that forest management will sequester more above-ground carbon than preservation over a 40 year period if the wood is used for products with an average half life greater than 5 years.     

Biomass yield,nitrogen response,and nutrient uptake of perennial bioenergy grasses in North Carolina

Although perennial grasses show considerable potential as candidates for lignocellulosic bioenergy production, these crops exhibit considerable variation in regional adaptability and yield. Giant miscanthus (Miscanthus × giganteus Greef & Deuter), Miscanthus sinensis Anderss. ‘Gracillimus’ and MH2006, plume grass (Saccharum arundinaceum Retz.), ravenna grass (Saccharum ravennae (L.) L.), switchgrass (Panicum virgatum L. ‘Alamo’), and giant reed (Arundo donax L.) field plots were established in 2008, treated with four nitrogen (N) fertilizer rates (0, 34, 67, 134 kg ha⁻¹ y⁻¹), and harvested annually in winter from 2008 to 2011. Giant reed, ‘Gracillimus’, switchgrass, MH2006, giant miscanthus and ravenna grass at the Mountain site produced mean dry matter yields of 22.8, 21.3, 20.9, 19.3, 18.4, and 10.0 Mg ha⁻¹ y−¹, respectively (averaged over the last two years). Dry matter yields at the Coastal site for giant reed, giant miscanthus, switchgrass, ravenna grass, and ‘Gracillimus’ were 27.4, 20.8, 20.1, 14.3, and 9.4 Mg ha⁻¹ y⁻¹, respectively (averaged over the last two years). Increasing N rates up to 134 kg N ha⁻¹ did not have a consistent significant effect on biomass production. High yields coupled with high mortality for plume grass at both sites indicates its potential as a bioenergy crop and need for continued improvement. Overall, the perennial grasses in this study had low nutrient removal, although giant reed and plume grass often removed significantly more N, P, K and S compared with Miscanthus spp. and switchgrass. Our results indicate that giant reed, giant miscanthus, and switchgrass are productive bioenergy crops across geographic regions of North Carolina.     

Overview analysis of bioenergy from livestock manure management in Taiwan

The emissions of greenhouse gases (GHGs) from the livestock manure are becoming significant energy and environmental issues in Taiwan. However, the waste management (i.e., anaerobic digestion) can produce the biogas associated with its composition mostly consisting of methane (CH₄), which is now considered as a renewable energy with emphasis on electricity generation and other energy uses. The objective of this paper was to present an overview analysis of biogas-to-bioenergy in Taiwan, which included five elements: current status of biogas sources and their energy utilizations, potential of biogas (methane) generation from livestock manure management, governmental regulations and policies for promoting biogas, benefits of GHGs (i.e., methane) emission reduction, and research and development status of utilizing livestock manure for biofuel production. In the study, using the livestock population data surveyed by the Council of Agriculture (Taiwan) and the emission factors recommended by the Intergovernmental Panel on Climate Change (IPCC), the potential of methane generation from livestock manure management in Taiwan during the period of 1995–2007 has been estimated to range from 36 to 56 Gg year⁻¹, indicating that the biogas (methane) from swine and dairy cattle is abundant. Based on the characteristics of swine manure, the maximum potential of methane generation could reach to around 400 Gg year⁻¹. With a practical basis of the total swine population (around 4300 thousand heads) from the farm scale of over 1000 heads, a preliminary analysis showed the following benefits: methane reduction of 21.5 Gg year⁻¹, electricity generation of 7.2 × 10⁷ kW-h year⁻¹, equivalent electricity charge saving of 7.2 × 10⁶ US$ year⁻¹, and equivalent carbon dioxide mitigation of 500 Gg year⁻¹.     

Runoff,sediment, nitrogen,and phosphorus losses from agricultural land converted to sweetgum and switchgrass bioenergy feedstock production in north Alabama

Renewable energy sources such as bioenergy crops have significant potential as alternatives to fossil fuels. Potential environmental problems arising from soil sediment and nutrient losses in runoff water from bioenergy crops need to be evaluated in order to determine the sustainability and overall feasibility of implementing bioenergy development strategies. This paper discusses runoff, sediment, N, and total P losses from agricultural land (continuous cotton (Gossypium hirsutum L.)) converted to short-rotation sweetgum (Liquidamber styraciflua L.) plantations with and without fescue (Festuca elatior L.) and switchgrass (Panicum virgatum L.) bioenergy crops, compared to corn (Zea mays L.), on a Decatur silt loam soil in north Alabama, from 1995 to 1999. Runoff volume was significantly correlated to total rainfall and sediment yield in each year, but treatment differences were not significant. Sweetgum plots produced the highest mean sediment yield of up to 800 kg ha⁻¹compared to corn and switchgrass plots, which averaged less than 200 kg ha⁻¹. Runoff NH₄⁺ N losses averaged over treatments and years for spring season (3.1 kg ha⁻¹) were three to five times those for summer, fall, and winter seasons. Runoff NO₃⁻ N for no-till corn and switchgrass plots in spring and summer were five to ten times that for sweetgum plots. No-till corn and switchgrass treatments had 2.4 and 2.1 kg ha⁻¹ average runoff total P, respectively, which were two to three times that for sweetgum treatments. Growing sweetgum with a fescue cover crop provides significantly lower risk of water pollution from sediment, runoff NH₄⁺ N, and NO₃⁻ N.     

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.     

Evaluation of bioenergy resources with a global land use and energy model formulated with SD technique

Bioenergy is expected to become one of the key energy resources for global sustainable development. However, bioenergy cannot be infinite, because the land area available for biomass production is limited and a certain amount of biomass must be reserved for food and materials. The purpose of this study is to evaluate global bioenergy potential: for this purpose, the authors developed a global land-use and energy model (GLUE) formulated using a SD (System Dynamics) technique. Through a simulation, the following results were obtained. (1) There will be a certain potential for energy crops harvested from surplus arable land in the developed regions of the world. However, care must be taken because the potential is sensitive to the global food supply and demand. (2) There will be a large bioenergy potential for biomass residues, such as cereal-harvesting residues, animal dung, roundwood felling residues, and timber scrap. The ultimate bioenergy potential, from all the biomass residues, will be 277 EJ/yr in A.D. 2100 in the world. (3) The mature-forest area in the developing regions decreases from 2.1 billion ha in 1990 to 0.8 billion ha in 2100, although it is assumed that the felling area is reforested completely after A.D. 2025. Thus, there will not be much room to obtain more fuelwood from forests in the developing regions.     

Potential to expand sustainable bioenergy from sugarcane in southern Africa

The Cane Resources Network for Southern Africa evaluated how bioenergy from sugarcane can support sustainable development and improve global competitiveness in the region. The assessment of six countries with good contemporary potential for expanding sugarcane cultivation described in this paper was part of their analysis. Its principal objective was to identify land where such production will not have detrimental environmental and/or socio-economic impacts. Geographic Information Systems (GIS) was used to interrogate 1 km² resolution protected area, land cover, climate, elevation and soil data sets. To avoid detrimental impacts on biodiversity, all categories of protected areas, closed canopy forests and wetlands were excluded. To safeguard food security, all areas under food and/or cash crop production were excluded. Areas unsuitable because of climate, terrain and soil constraints were also excluded. The assessment found that almost 6 million hectares of suitable land is available in these countries, clearly suggesting that ‘land’ is unlikely to be a limiting factor in harnessing sugarcane’s bioenergy potential in the region. However, land identified as such in this study needs to be verified using better resolution, preferably ground, information.     

Fermentative bioenergy production from distillers grains using mixed microflora

The feasibility of hydrogen production from distillers grains substrate, an industrial cellulosic waste, was investigated. A substrate concentration of 80 g/L gave the maximum production at 50 °C and pH of 6.0 using sewage sludge. Four controllable factors with three levels: seed sludge (two sewage sludges and cow dung), temperature (40, 50, and 60 °C), pH (6, 7 and 8) and seed pretreatment (none, heat, and acid) were selected in Taguchi experimental design to optimize fermentation conditions. The peak hydrogen and ethanol productions were found with heat-treated cow dung seed, substrate concentration 80 g/L, 50 °C and pH 6. The peak hydrogen production rate and hydrogen yield were 7.9 mmol H₂/L/d and 0.40 mmol H₂/g-COD respectively whereas the peak ethanol production was 3050 mg COD/L and rate 0.22 g EtOH/L/d. A total bioenergy yield of 41 J/g substrate was obtained which was 21% and 79% from hydrogen and ethanol respectively.     

中国农村生物质能消费的CO_2排放量估算

借助国际通用的CO2排放鼍计算方法,利用1996～2006年中国农村可再生能源统计资料,对中同农村生物质能消费的CO2排放情况及其空间分布进行分析探讨.结果表明,中国农村生物质能消费的CO2排放总量达到7.25×108t,约占农村生活能源消费CO22排放量的65%,占全国温窜气体总排放量的11.2%,其中秸秆、薪柴等传统生物质能利用方式贡献较大,可达98.64%～99.74%;中国农村生物质能消费CO2排放量的空间分布不均,四川、广西等省CO2排放量大,属超重排放区域,北京、天津、上海、西藏、青海等省(市、区)排放量小,属轻排放区域:区域生物质资源条件和经济社会水平是影响农村生物质能消费CO22排放的主要因素.     

Technological learning in bioenergy systems

The main goal of this article is to determine whether cost reductions in different bioenergy systems can be quantified using the experience curve approach, and how specific issues (arising from the complexity of biomass energy systems) can be addressed. This is pursued by case studies on biofuelled combined heat and power (CHP) plants in Sweden, global development of fluidized bed boilers and Danish biogas plants. As secondary goal, the aim is to identify learning mechanisms behind technology development and cost reduction for the biomass energy systems investigated. The case studies reveal large difficulties to devise empirical experience curves for investment costs of biomass-fuelled power plants. To some extent, this is due to lack of (detailed) data. The main reason, however, are varying plant costs due to differences in scale, fuel type, plant layout, region etc. For fluidized bed boiler plants built on a global level, progress ratios (PRs) for the price of entire plants lies approximately between 90–93% (which is typical for large plant-like technologies). The costs for the boiler section alone was found to decline much faster. The experience curve approach delivers better results, when the production costs of the final energy carrier are analyzed. Electricity from biofuelled CHP-plants yields PRs of 91–92%, i.e. an 8–9% reduction of electricity production costs with each cumulative doubling of electricity production. The experience curve for biogas production displays a PR of 85% from 1984 to the beginning of 1990, and then levels to approximately 100% until 2002. For technologies developed on a local level (e.g. biogas plants), learning-by-using and learning-by-interacting are important learning mechanism, while for CHP plants utilizing fluidized bed boilers, upscaling is probably one of the main mechanisms behind cost reductions.     

沼肥对保护地番茄生长发育及其产量的影响

采用二裂式区组设计的方法,以番茄为供试作物,以沼肥（沼液、沼渣）、猪粪和化肥为肥料,研究了不同施肥措施对番茄生长发育及其产量的影响。结果表明：与施用化肥相比,施用沼液的番茄植株平均株高及根系体积有所增加,番茄产量略有降低;与施用猪粪相比,施用沼渣可促进植株茎秆的健壮生长及根系发育,番茄产量提高20．8％;与沼渣和化肥配合施用相比,沼渣与沼液配合施用促进了番茄植株的生长发育,其植株生长稳健,根系发达,而且番茄产量增加;与猪粪和化肥配合施用相比,猪粪与沼液配合施用促进了番茄植株的生长发育,其株高较高、茎秆粗壮、根系发达,但番茄产量下降。     

From the global efforts on certification of bioenergy towards an integrated approach based on sustainable land use planning

This paper presents an overview of 67 ongoing certification initiatives to safeguard the sustainability of bioenergy. Most recent initiatives are focused on the sustainability of liquid biofuels. Content-wise, most of these initiatives have mainly included environmental principles. Despite serious concerns in various parts of the world on the socio-economic impacts of bioenergy production, these are generally not included in existing bioenergy initiatives. At the same time, the overview shows a strong proliferation of standards. The overview shows that certification has the potential to influence direct, local impacts related to environmental and social effects of direct bioenergy production. Key recommendations to come to an efficient certification system include the need for further harmonization, availability of reliable data and linking indicators on a micro, meso and macro levels. Considering the multiple spatial scales, certification should be combined with additional measurements and tools on a regional, national and international level. The role of bioenergy production on indirect land use change (ILUC) is still very uncertain and current initiatives have rarely captured impacts from ILUC in their standards. Addressing unwanted LUC requires first of all sustainable land use production and good governance, regardless of the end-use of the product. It is therefore recommended to extend measures to mitigate impacts from LUC to other lands and feedstock.     

On sustainability of bioenergy production: Integrating co-emissions from agricultural intensification

Biomass from cellulosic bioenergy crops is seen as a substantial part of future energy systems, especially if climate policy aims at stabilizing CO₂ concentration at low levels. However, among other concerns of sustainability, the large-scale use of bioenergy is controversial because it is hypothesized to increase the competition for land and therefore raise N₂O emissions from agricultural soils due to intensification. We apply a global land-use model that is suited to assess agricultural non-CO₂ GHG emissions. First, we describe how fertilization of cellulosic bioenergy crops and associated N₂O emissions are implemented in the land-use model and how future bioenergy demand is derived by an energy-economy-climate model. We then assess regional N₂O emissions from the soil due to large-scale bioenergy application, the expansion of cropland and the importance of technological change for dedicated bioenergy crops. Finally, we compare simulated N₂O emissions from the agricultural sector with CO₂ emissions from the energy sector to investigate the real contribution of bioenergy for low stabilization scenarios.As a result, we find that N₂O emissions due to energy crop production are a minor factor. Nevertheless, these co-emissions can be significant for the option of removing CO₂ from the atmosphere (by combining bioenergy use with carbon capture and storage (CCS) options) possibly needed at the end of the century for climate mitigation. Furthermore, our assessment shows that bioenergy crops will occupy large shares of available cropland and will require high rates of technological change at additional costs.