Economic and CO2 mitigation impacts of promoting biomass heating systems: An input–output study for Vorarlberg, Austria

This paper reports on an empirical investigation about the economic and CO₂ mitigation impacts of bioenergy promotion in the Austrian federal province of Vorarlberg. We study domestic value-added, employment, and fiscal effects by means of a static input–output analysis. The bioenergy systems analysed comprise biomass district heating, pellet heating, and automated wood chip heating systems, as well as logwood stoves and boilers, ceramic stoves, and buffer storage systems. The results indicate that gross economic effects are significant, regarding both investment and operation of the systems, and that the negative economic effects caused by the displacement of conventional decentralised heating systems might be in the order of 20–40%. Finally, CO₂ mitigation effects are substantial, contributing already in 2004 around 35% of the 2010 CO₂ mitigation target of the Land Vorarlberg for all renewable energy sources.     

A bottom-up assessment and review of global bio-energy potentials to 2050

In this article, a model for estimating bioenergy production potentials in 2050, called the Quickscan model, is presented. In addition, a review of existing studies is carried out, using results from the Quickscan model as a starting point. The Quickscan model uses a bottom-up approach and its development is based on an evaluation of data and studies on relevant factors such as population growth, per capita food consumption and the efficiency of food production. Three types of biomass energy sources are included: dedicated bioenergy crops, agricultural and forestry residues and waste, and forest growth. The bioenergy potential in a region is limited by various factors, such as the demand for food, industrial roundwood, traditional woodfuel, and the need to maintain existing forests for the protection of biodiversity. Special attention is given to the technical potential to reduce the area of land needed for food production by increasing the efficiency of food production. Thus, only the surplus area of agricultural land is included as a source for bioenergy crop production. A reference scenario was composed to analyze the demand for food. Four levels of advancement of agricultural technology in the year 2050 were assumed that vary with respect to the efficiency of food production. Results indicated that the application of very efficient agricultural systems combined with the geographic optimization of land use patterns could reduce the area of land needed to cover the global food demand in 2050 by as much as 72% of the present area. A key factor was the area of land suitable for crop production, but that is presently used for permanent grazing. Another key factor is the efficiency of the production of animal products. The bioenergy potential on surplus agricultural land (i.e. land not needed for the production of food and feed) equaled 215–1272 EJ yr⁻¹, depending on the level of advancement of agricultural technology. The bulk of this potential is found in South America and Caribbean (47–221 EJ yr⁻¹), sub-Saharan Africa (31–317 EJ yr⁻¹) and the C.I.S. and Baltic States (45–199 EJ yr⁻¹). Also Oceania and North America had considerable potentials: 20–174 and 38–102 EJ yr⁻¹, respectively. However, realization of these (technical) potentials requires significant increases in the efficiency of food production, whereby the most robust potential is found in the C.I.S. and Baltic States and East Europe. Existing scenario studies indicated that such increases in productivity may be unrealistically high, although these studies generally excluded the impact of large scale bioenergy crop production. The global potential of bioenergy production from agricultural and forestry residues and wastes was calculated to be 76–96 EJ yr⁻¹ in the year 2050. The potential of bioenergy production from surplus forest growth (forest growth not required for the production of industrial roundwood and traditional woodfuel) was calculated to be 74 EJ yr⁻¹ in the year 2050.     

A novel approach to simulate growth of multi-stem willow in bioenergy production systems with a simple process-based model (3PG)

An important requirement for commercialization of willow biomass production in short-rotation crop (SRC) plantations is the reliable and cost-efficient estimation of biomass yield. Predictions and simulations of willow stand biomass have been problematic due to issues with modeling the multi-stem growth form of willow. The aim of this paper was to develop a new approach for managing allometric measurements from multi-stemmed willow for stand growth simulations. The 3PG model (Physiological Principles in Predicting Growth) was parameterized for willow and was used for biomass yield simulation for an entire 22-yr cycle (seven 3-yr rotations) of willow in SRC plantations. The multi-stemmed growth form was transformed into a single-stem modeling form by deriving whole plant willow allometric relationships using detailed stem-level measurements of basal area, stem biomass and volume. 3PG model predictions for plant diameter, height, biomass, and stand biomass and volume were within the 95% confidence range of mean plot values. Model simulations showed that after seven 3-yr rotations only 20% of planted cuttings would survive (a decrease from 15,152 to 3022 plants ha⁻¹), but stand volume would increase continuously with each subsequent rotation. 3PG predictions for cumulative (for 22 yr) aboveground biomass was 272 Mg ha⁻¹ and mean annual yield was 12 Mg ha⁻¹ yr⁻¹, comparing favorably with other findings. To our knowledge, this work is the first where the 3PG model was calibrated and used for willow species. Once parameterized for a specific willow clone, 3PG can predict biomass accumulation for any agricultural land in North America using only available soil and climate data.     

Converting Eucalyptus biomass into ethanol: Financial and sensitivity analysis in a co-current dilute acid process. Part II

The technical and financial performance of high yield Eucalyptus biomass in a co-current dilute acid pretreatment followed by enzymatic hydrolysis process was simulated using WinGEMS^® and Excel^®. Average ethanol yield per dry Mg of Eucalyptus biomass was approximately 347.6 L of ethanol (with average carbohydrate content in the biomass around 66.1%) at a cost of $0.49 L⁻¹ of ethanol, cash cost of ∼ $0.46 L⁻¹ and CAPEX of $1.03 L⁻¹ of ethanol. The main cost drivers are: biomass, enzyme, tax, fuel (gasoline), depreciation and labor. Profitability of the process is very sensitive to biomass cost, carbohydrate content (%) in biomass and enzyme cost. Biomass delivered cost was simulated and financially evaluated in Part I; here in Part II the conversion of this raw material into cellulosic ethanol using the dilute acid process is evaluated.     

The current bioenergy production potential of semi-arid and arid regions in sub-Saharan Africa

This article assesses the current technical and economic potential of three bioenergy production systems (cassava ethanol, jatropha oil and fuelwood) in semi-arid and arid regions of eight sub-Saharan African countries. The results indicate that the availability of land for energy production ranges from 2% (1.3 Mha) of the total semi-arid and arid area in South Africa to 21% (12 Mha) in Botswana. Land availability for bioenergy production is restricted mainly by agricultural land use, but also by steep slopes and biodiversity protection. The current total technical potential for the semi-arid and arid regions of the eight countries is calculated to be approximately 300 PJ y⁻¹ for cassava ethanol production, 600 PJ y⁻¹ for jatropha biodiesel or 4000 PJ y⁻¹ for fuelwood. The analysis of economic potentials shows that in many semi-arid regions, cassava ethanol, jatropha oil and fuelwood can compete economically with the reference energy sources. However, fuelwood, jatropha oil, and cassava ethanol production costs in most arid regions of sub-Saharan Africa are often above average national market prices of gasoline, diesel, and fuelwood. Nevertheless, for example, in arid Kenya 270 PJ could be produced annually with fuelwood at production costs of less than 3 US$ GJ⁻¹. Despite high production costs, it is important to investigate and invest in sustainable bioenergy production in semi-arid and arid regions of sub-Saharan Africa because of its potential to drive rural economic and social development.     

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.     

Evaluation of stainless steel cathodes and a bicarbonate buffer for hydrogen production in microbial electrolysis cells using a new method for measuring gas production

Microbial electrolysis cells (MECs) are often examined for hydrogen production using non-sustainable phosphate buffered solutions (PBS), although carbonate buffers have been shown to work in other bioelectrochemical systems with a platinum (Pt) catalyst. Stainless steel (SS) has been shown to be an effective catalyst for hydrogen evolution in MECs, but it has not been tested with carbonate buffers. We evaluated the combined using of SS cathodes and a bicarbonate buffer (BBS) at the applied voltages of 0.5, 0.7 and 0.9 V using a new inexpensive method for measuring gas production called the gas bag method (GBM). This method achieved an average error of only 5.0% based on adding known volumes of gas to the bag. Using the GBM, hydrogen production with SS and a BBS was 26.6 ± 1.8 mL which compared well to 26.4 ± 2.8 mL using Pt and BBS, and 26.8 ± 2.5 mL with a Pt cathode and PBS. Electrical energy efficiency was highest with a SS cathode and BBS at 159 ± 17%, compared to 126 ± 14% for the Pt cathode and BBS, and 134 ± 17% for a Pt cathode and PBS. The main disadvantage of the SS was a lower gas production rate of 1.1 ± 0.3 m³ H₂-m⁻³ d⁻¹ with BBS and 1.2 ± 0.3 m³ H₂-m⁻³ d⁻¹ with PBS, compared to 1.7 ± 0.4 m³ H₂-m⁻³ d⁻¹ with Pt and PBS. These results show that the GBM is an effective new method for measuring gas production of anaerobic gas production processes, and that SS and bicarbonate buffers can be used to effectively produce hydrogen in MECs.     

Simultaneous coproduction of hydrogen and methane from sugary wastewater by an “ACSTRH–UASBMet” system

A two-phase “ACSTR_H–UASB_Met” system has been investigated at the stepwise decreased HRT for the simultaneous production of hydrogen and methane in this study. Hydrogen could be continuously produced from the two-phase hydrogen fermentation of sugary wastewater in ACSTR and effluents from hydrogen fermentation were converted into methane in UASB reactor. At optimum conditions (HRT_H: 5 h, HRT_Met: 15 h), the highest hydrogen production rate of 5.69 (±0.06) mmol L⁻¹ h⁻¹ was obtained from sugary wastewater and methane was continuously produced from effluents of hydrogen fermentation with a production rate of 3.74 (±0.13) mmol L⁻¹ h⁻¹. The total bioenergy recovery by coproduction of hydrogen and methane from sugary wastewater reached 19.37 W and a total of 92.41% of substrate was converted to the biogas (hydrogen and methane) with two-phase anaerobic fermentation.     

Nitrogen mineralization of sewage sludge and composted poultry manure applied to willow in a greenhouse experiment

Nitrogen requirements for production of intensively cultured willow for use as a bioenergy crop coupled with the need for safe disposal of nutrient rich organic wastes provide an opportunity to reduce costs associated with bioenergy plantations. In order to minimize N leaching from sites treated with organic wastes, knowledge of the rate of N mineralization is needed. The objective of this study was to assess N mineralization rates of four organic residuals in a controlled greenhouse environment: composted poultry manure, composted sewage sludge, and anaerobically digested sewage sludge from two different municipalities. Thirty-six weeks after application, disappearance of the mass initially applied ranged from 20% to 50%. Gross nitrogen mineralization rate (N mass released expressed as a percentage of initially applied N) ranged from 12% to 57%. Non-composted treatments released greater amounts of nitrogen than composted treatments. Within composted treatments, net N release was estimated as 325 kgNha⁻¹ for poultry manure and 86 kgNha⁻¹ for sewage sludge. Syracuse and New York City sewage sludges, with 57% and 30% gross N release rates respectively, provided approximately 360 and 240 kg plant available Nha⁻¹, respectively. These estimates of N release suggest that the application rates could be halved and that sufficient N would be provided to meet crop needs and reduce leaching losses.     

Creation of regional added value by regional bioenergy resources

In debates about the positive effects of renewable and bioenergy projects the aspect of generating regional added value is discussed widely. But the real effects, generated by this regional added value stayed up to now on a non-measurable level. In order to expedite the calculation of these important figures, the author presents a field tested method for confidently arriving at useful values. This methodology takes into consideration the ecological, economical and social impact of a given biomass project's implementation. The model enables a comparison between the different renewable energy plants as well as between them and plants and technology of competing alternatives. Regional authorities are hereby enabled to count on a tool for confidently measuring the possible results of various bioenergy utilization technologies. With this knowledge at hand, they could then take qualified decisions towards positive effects for their region. The developed tool allows the definition of adjustable parameters, and therefore it is able to influence the regional framework regarding a more sustainable development.