Seasonal time of switchgrass (Panicum virgatum L.) harvest affects yield and biofuel quality and balancing these two components may vary depending on conversion system. A field study compared fall and spring harvest measuring biomass yield, element concentration, carbohydrate characterization, and total synthetic gas production as indicators of biofuel quality for direct combustion, ethanol production, and gasification systems for generation of energy. Switchgrass yields decreased almost 40% (from about 7–4.4 Mg ha 21 ) in winters with above average snowfall when harvest was delayed over winter until spring. The moisture concentration also decreased (from about 350– 70 g kg 21 ) only reaching low enough levels for safe storage by spring. About 10% of the yield reduction during winter resulted from decreases in tiller mass; however, almost 90% of the yield reduction was due to an increase in biomass left behind by the baler. Mineral element concentrations generally decreased with the delay in harvest until spring. Energy yield from gasification did not decrease on a unit biomass basis, whereas ethanol production was variable depending on the assessment method. When expressed on a unit area basis, energy yield decreased. Biofuel conversion systems may determine harvest timing. For direct combustion, the reduced mineral concentrations in spring-harvested biomass are desirable. For ethanol fermentation and gasification systems, however, lignocellulose yield may be more important. On conservations lands, the wildlife cover provided by switchgrass over the winter may increase the desirability of spring harvest along with the higher biofuel quality.

Biomass Yield and Biofuel Quality of Switchgrass Harvested in Fall or Spring

Clifton-Brown, J. C., Breuer, J., Jones, M. B. (2007). Carbon mitigation by the energy crop, Miscanthus. Global Change Biology. 13 (11), 2296-2307 Sponsorship: EU JOUB-0069 / AIR-CT92-0294 RAE2008

Carbon mitigation by the energy crop, Miscanthus

John C. Clifton-Brown, Paul F. Stampfl, Michael B. Jones (2004). Miscanthus biomass production for energy in Europe and its potential contribution to decreasing fossil fuel carbon emissions. Global Change Biology, 10 (4)509-518 RAE2008

Miscanthus biomass production for energy in Europe and its potential contribution to decreasing fossil fuel carbon emissions

The preceding decades witnessed hydrothermal processes being actively utilized all over the world, specifically in the developed zones. Their optimum usage is primarily sought for in terms of conversion of biomass into valuable solid, liquid and gaseous fuels. Indeed, Hydrothermal carbonization (HTC) is an effective and environment friendly technique; it possesses extensive potential towards producing high-energy density solid fuels. However, the production and quality of solid fuels from HTC depends upon several parameters; temperature, feed type, residence time, pressure and catalyst being the eminent ones. This study investigates the influence of operating parameters on solid fuel production during HTC. The biomass quality has also been analyzed in HTC by extending existing literature work through experiments that have been performed. Data including chemical composition, heating value, proximate analysis and ultimate analysis for different types of biomass was consequently collected and analyzed. It was found that reaction temperature, residence time and type of feed material are the primary factors that influence the HTC process. At higher temperatures, lower solid product is obtained; the carbon content increases, whilst the hydrogen and oxygen content decrease. Further, it has been found that higher lignin content in biomass leads to an increased solid fuel production.

An overview of effect of process parameters on hydrothermal carbonization of biomass

Bioenergy from permanent grassland--a review: 2. Combustion.

Delayed harvest of miscanthus—influences on biomass quantity and quality and environmental impacts of energy production

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Scientists Against War: A Plea to World Leaders for Better Governance

Thermal energy storage is a key technology that can support the transformation of our energy system to renewable energy sources. Compared to sensible energy storage systems commonly used in heating, ventilation and air conditioning, phase change material (PCM) based storage systems offer significantly higher storage capacities due to the latent energy of the solid-liquid phase change. In this work, we analyzed a PCM storage using commercially available PCM modules with a special, non-spherical shape. For the future performance analysis of the storage in a cooling application by means of system simulations, a simulation model is needed that enables the correct prediction of the thermal behaviour under different operating conditions. For this purpose, a PCM storage model originally developed for PCM spheres was used and parametrized with regard to the non-spherical module shape. The numerical results agreed well with the results of a series of 19 charging and discharging tests conducted under a wide range of operating conditions. Regarding the thermal power, the highest root mean square error of all tests performed was 0.4 kW for heating and 0.98 kW for cooling, while it was 0.68 K and 0.86 K, respectively, for the in- and outlet temperatures. The observed levels of deviation for the cooling process were generally higher than those for heating, which was due to a quite simple modelling of the supercooling phenomenon. 

A Heinz

Papers

Delayed harvest of miscanthus—influences on biomass quantity and quality and environmental impacts of energy production

Scientists Against War: A Plea to World Leaders for Better Governance

Numerical modelling and experimental testing of a thermal storage system with non-spherical macro-encapsulated phase change material modules