Development and application of BioFeed model for optimization of herbaceous biomass feedstock production

An efficient and sustainable biomass feedstock production system is critical for the success of the biomass based energy sector. An integrated systems analysis framework to coordinate various feedstock production related activities is, therefore, highly desirable. This article presents research conducted towards the creation of such a framework. A breadth level mixed integer linear programming model, named BioFeed, is proposed that simulates different feedstock production operations such as harvesting, packing, storage, handling and transportation, with the objective of determining the optimal system level configuration on a regional basis. The decision variables include the design/planning as well as management level decisions. The model was applied to a case study of switchgrass production as an energy crop in southern Illinois. The results illustrated that the total cost varied between 45 and 49 $ Mg⁻¹ depending on the collection area and the sustainable biorefinery capacity was about 1.4 Gg d⁻¹. The transportation fleet consisted of 66 trucks and the average utilization of the fleet was 86%. On-farm covered storage of biomass was highly beneficial for the system. Lack of on-farm open storage and centralized storage reduced the system profit by 17% and 5%, respectively. Increase in the fraction of larger farms within the system reduced the cost and increased the biorefinery capacity, suggesting that co-operative farming is beneficial. The optimization of the harvesting schedule led to 30% increase in the total profit. Sensitivity analysis showed that the reduction in truck idling time as well as increase in baling throughput and output density significantly increased the profit.     

Energy crops in Ireland: Quantifying the potential life-cycle greenhouse gas reductions of energy-crop electricity

This study uses life-cycle assessment (LCA) to compare greenhouse gas (GHG) emissions from dominant agricultural land uses, and peat and coal electricity generation, with fuel-chains for Miscanthus and short-rotation-coppice willow (SRCW) electricity. A simple scenario was used as an example, where 30% of peat and 10% of coal electricity generation was substituted with co-fired Miscanthus and SRCW, respectively. Miscanthus and SRCW cultivation were assumed to replace sugar-beet, dairy, beef-cattle and sheep systems. GHG emissions of 1938 and 1346 kg CO₂ eq. ha⁻¹ a⁻¹ for Miscanthus and SRCW cultivation compared with between 3494 CO₂ eq. ha⁻¹ a⁻¹ for sugar-beet cultivation and 12,068 CO₂ eq. ha⁻¹ a⁻¹ for dairy systems. Miscanthus and SRCW fuel chains emitted 0.131 and 0.132 kg CO₂ eq. kWh⁻¹ electricity exported, respectively, compared with 1.150 and 0.990 kg CO₂ eq. kWh⁻¹ electricity exported for peat and coal fuel chains. 1.48 Mt CO₂ eq. a⁻¹ was saved from electricity production, and 0.42 Mt CO₂ eq. a⁻¹ was saved from displaced agriculture and soil C-sequestration. The total reduction of 1.9 Mt CO₂ eq. a⁻¹ represents 2.8% of Ireland's 2004 GHG emissions, but was calculated to require just 1.7% of agricultural land area and displace just 1.2% of the dairy herd (based on conservative Miscanthus and SRCW combustible-yield estimates of 11.7 and 8.81 t ha⁻¹ a⁻¹ dry matter, respectively). A 50% increase in cultivation emissions would still result in electricity being produced with an emission burden over 80% lower than peat and coal electricity. Lower yield assumptions had little impact on total GHG reductions for the scenario, but required substantially greater areas of land. It was concluded that energy-crop utilisation would be an efficient GHG reduction strategy for Ireland.     

Soil organic carbon changes in the cultivation of energy crops: Implications for GHG balances and soil quality for use in LCA

The environmental impact of different land-use systems for energy, up to the farm or forest “gate”, has been quantified with Life Cycle Assessment (LCA). Four representative crops are considered: OilSeed Rape (OSR), Miscanthus, Short-Rotation Coppice (SRC) willow and forest residues. The focus of the LCA is on changes in Soil Organic Carbon (SOC) but energy use, emissions of GreenHouse Gases (GHGs), acidification and eutrophication are also considered. In addition to providing an indicator of soil quality, changes in SOC are shown to have a dominant effect on total GHG emissions. Miscanthus is the best land-use option for GHG emissions and soil quality as it sequesters C at a higher rate than the other crops, but this has to be weighed against other environmental impacts where Miscanthus performs worse, such as acidification and eutrophication. OSR shows the worst performance across all categories. Because forest residues are treated as a by-product, their environmental impacts are small in all categories. The analysis highlights the need for detailed site-specific modelling of SOC changes, and for consequential LCAs of the whole fuel cycle including transport and use.     

Hope and skepticism: Farmer and local community views on the socio-economic benefits of agricultural bioenergy

U.S. government policies and programs promoting agricultural bioenergy development have tended to prioritize national goals of energy security, economic growth and environmental improvement, while marginalizing the local experiences, views and concerns of farmers and rural communities that will produce the needed energy crops. Based on qualitative field interviews with 48 farming and non-farming participants in two switchgrass bioenergy projects (in southern Iowa and in northeastern Kentucky), this paper examines local perspectives on the potential opportunities, drawbacks, and tradeoffs of the emerging agricultural bioeconomy for rural people and places. Individual project participants expressed both positive and negative perceptions about the impacts of the agricultural bioeconomy, with local and regional revitalization being the benefit most desired and also least expected. Skepticism about the social impacts of the agricultural bioeconomy often stemmed from observations of corporate control in agriculture more generally. This research suggests that narrow instrumental views of farmers and rural communities as technical providers of energy feedstocks can be misleading, because they omit the local social and cultural context that complicates rural responses and receptivity to the development of the agricultural bioeconomy.     

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

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

Hydrothermal carbonization of biomass as a route for the sequestration of CO2: Chemical and structural properties of the carbonized products

A highly functionalized carbonaceous material (hydrochar) was obtained by means of the hydrothermal carbonization (250 °C) of two representative types of biomass, i.e. eucalyptus sawdust and barley straw. This product has a brown colour; it contains around 50-60% of the carbon originally present in the biomass and it is composed of particles that retain the cellular appearance of the raw material. These particles are covered by microspheres (1-10 ??m) which were probably formed as a consequence of the transformation of the cellulose fraction. From a chemical point of view, the hydrochar products have a high degree of aromatization and they contain a large amount of oxygen-containing groups (i.e. carbonyl, carboxylic, hydroxyl, quinone, ester, etc) as was confirmed by Raman, IR and XPS spectroscopic techniques. The presence of these oxygen functionalities on the surface of the hydrochar particles explains their high water affinity (hydrophilic properties). On the basis of the highly condensed chemical nature of the hydrochar products, we postulated that this material has a recalcitrant nature that could lead to a significant increase in carbon turnover time in relation to the biomass. This suggests an important route for the sequestration of CO₂ present in the atmosphere.     

Effect of hydrogen addition on criteria and greenhouse gas emissions for a marine diesel engine

Hydrogen remains an attractive alternative fuel to petroleum and a number of investigators claim that adding hydrogen to the air intake manifold of a diesel engine will reduce criteria emissions and diesel fuel consumption. Such claims are appealing when trying to simultaneously reduce petroleum consumption, greenhouse gases and criteria pollutants. The goal of this research was to measure the change in criteria emissions (CO, NO_x, and PM_2.5) and greenhouse gases such as carbon dioxide (CO₂), using standard test methods for a wide range of hydrogen addition rates. A two-stroke Detroit Diesel Corporation 12V-71TI marine diesel engine was mounted on an engine dynamometer and tested at three out of the four loads specified in the ISO 8178-4 E3 emission test cycle and at idle. The engine operated on CARB ultra-low sulfur #2 diesel with hydrogen added at flow rates of 0, 22 and 220 SLPM.     

Predictive models for dry weight estimation of above and below ground biomass components of Populus deltoides in India: Development and comparative diagnosis

This article concentrates on development of statistical models for prediction of biomass components (above and below ground) of standing trees of Populus deltoides. Twenty seven trees (three each from age one to nine years) were destructively harvested, separated, sorted, sub-sampled, dried to constant weight at 60 °C and weighted for biomass components (leaf, twig, branch, bole, stump root, lateral root, fine root). Harvesting in a similar manner, was continued annually up to nine years of tree age and thus in all 27 sampled trees were available for analysis and fitting of models. Diameter at breast height (dbh) alone was a very good predictor of dry weight and accordingly the height was not included in the model. Various functions viz (linear, allometric, logistic, gompertz and chapman-richards), were attempted for dry weight estimation. The linear model, though easiest to fit, suffered from the ‘negative estimation problem’, specifically for the lower range of explanatory variate. Of the remaining non-linear models, the allometric model outperformed the others on the basis of validation criterions. The value of R² ranged from 0.95 to 0.99, for the allometric models fitted on various biomass components. The proposed models can be used for prediction of component wise dry biomass of P. deltoides for a wide range of dbh values (1-50 cm) at one end and can also help farmers in the choice of economical harvest rather than the traditional physical rotation. In addition, they can be used in carbon sequestration studies, which needs complete biomass estimation.     

Emissions targeting and planning: An application of CO2 emissions pinch analysis (CEPA) to the Irish electricity generation sector

This paper outlines the past analysis and projected planning of the Irish electricity generation sector using an extension of a novel methodology based on a graphical optimisation concept. The main two adaptations/extensions to the current form of the methodology are proposed as both the forecasting adaptation and the extension that accounts for the dynamic nature of electricity supply–demand. The determination of an optimal energy resource (OER) mix (or optimal fuel mix) for the sector will look to give guidelines towards fulfilling the sector's Kyoto targets, as well as yielding a possible approach for other sectors to follow in the future. Data pertaining to the sector for the year 2005 was taken in order to illustrate the analysis and forecasting procedures.