Energy from agricultural residues

The segment concerned with thermal energy from agricultural residues is small and localized at the present time. Only a few types of agricultural residues, such as nut shells and corn cobs, are being utilized for the production of energy. Corporate activities are focused upon the use of agricultural residues which are low in moisture content, where the residues are a by-product of another operation, and where they are accumulated in a central location. 

The Renewables-Intensive Global Energy Scenario (RIGES) predicts a primary energy potential from biomass resources for Western Europe to be 14160 PJ/year by 2025 and 14 170 PJ/year by 2050 (Johansson et al., 1993). Thereby the biomass potential comprises resources from wood, energy crops, agricultural residues and industrial biomass residues. The estimates are based on the biomass production at that time in combination with assumptions of future growth rates. 

Hoogwijk et al. (2005) assume the biomass energy potential in Western Europe from energy crops, agricultural residues, forest residues and industrial biogenic residues to be of the order of 10000 PJ/year and 16000 PJ/year by 2050. The analysis is based on the IMAGE 2.2 model using the four scenarios from the Special Report on Emissions Scenarios (SRES), (Nakicenovic, 2000) as main assumptions for the included food demand and supply. 

Fig. 1.15 Key global biomass resources from agricultural residues, wood, and herbaceous energy crops. (A. J. Ragauskas et al., Science, 311,484 (2006). Reprinted with permission from AAAS [7]).

Specialised forms of energy recovery from agricultural residues are feasible, but are mitigated against in general by the costs of collection. This reflects the inherent storage... 

Although most ethanol is now produced from corn, research has been done on producing this type of alcohol fuel from cellulosic biomass products including energy crops, forest and agricultural residues, and MSW, which would provide much cheaper feedstocks. The process of chemically converting these cellulosic biomass feedstocks is more involved and until this process can be simplified the price of ethanol will remain high. 

These systems offer the opportunity to produce hydrogen from renewable resources in the mid-term (five to ten years). Using agricultural residues and wastes, or biomass specifically grown for energy uses, hydrogen can be produced using a variety of processes. 

The list of plants, by-products and waste materials that can potentially be used as feedstock is almost endless. Major resources in biomass include agricultural crops and their waste by-products, lignocellulosic products such as wood and wood waste, waste from food processing and aquatic plants and algae and effluents produced in the human habitat. Moderately dried wastes such as wood residue, wood scrap and urban garbage can be directly burned as fuel. Energy from water-containing biomass... 

Generally, two types of biomass resources can be considered in the discussion on renewable energy feedstock (1) primary biomass, such as energy crops, including switchgrass, poplar, and willow, and (2) biomass residues (primary when derived from wood or processed agricultural biomass secondary when derived from food or fiber processing by-products, or animal waste and tertiary when derived from urban residues).21... 

Development of other densification methods for certain agricultural residues is expected to lead to improvements in soil growth characteristics as well as advanced residue recovery systems for energy applications. For example, cotton is a major crop in the state of Arizona. State law requires that cotton plant residue must be buried to prevent it from serving as an overwintering site for insect pests such as the pink bollworm. Research is underway to develop two... 

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