Economic and environmental impacts of an integrated-state anaerobic digestion system to produce compressed natural gas from organic wastes and energy crops

Production of methane via anaerobic digestion of energy crops and organic wastes would benefit society by providing a clean fuel from renewable feedstocks. This could replace fossil fuel-derived energy and reduce its environmental impacts, including global warming and acid rain. Although biomass energy is more costly than fossil fuel-derived energy, trends to limit carbon dioxide and other emissions through regulations, carbon taxes, and subsidies of biomass energy would make it cost competitive. Methane derived from anaerobic digestion is competitive in efficiencies and costs with other biomass energy forms including heat, synthesis gases, and ethanol. The objective of this paper is to review the results and conclusions of research on biomass energy conducted under the sponsorship of the gas industry with periodic co-funding from other agencies. The scope of this program was to determine the technical and economic feasibility of production of substitute natural gas (SNG) from marine and terrestrial biomass and organic wastes using anaerobic digestion as a conversion process. This work began in 1968 and continued until about 1990, ending as a result of low energy prices in the U.S. and reduced emphasis on renewable energy. For each of these feedstock categories, growth or collection (in the case of wastes), harvesting, conversion by anaerobic digestion, and systems and economic analysis were addressed. More recently the potential use of anaerobic digestion for stabilization and recovery of nutrients from solid wastes during space missions was studied with funding from NASA. The application of this process for that function as well as treatment of wastewater and waste gases generated during space missions is addressed.

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Comparison of the environmental performance of different treatment scenarios for the main phosphorus recycling sources

Renewable Agriculture and Food Systems ◽

10.1017/s1742170517000515 ◽

2017 ◽

Vol 34 (04) ◽

pp. 349-362 ◽

Cited By ~ 3

Author(s):

Stefan Josef Hörtenhuber ◽

Michaela Clarissa Theurl ◽

Kurt Möller

Keyword(s):

Anaerobic Digestion ◽

Environmental Impacts ◽

Environmental Performance ◽

Treatment Options ◽

Organic Wastes ◽

Direct Application ◽

Sequestration Potential ◽

P Recycling ◽

P Fertilizers ◽

Lca Results

AbstractEfficient phosphorus (P) recycling from rural and urban areas is becoming an increasing issue due to the scarcity of natural P deposits. Based on a life cycle assessment (LCA), we analyzed the environmental performance of 17 different P supply and recycling approaches from urban wastes, biosolids and slaughterhouse wastes compared with the two conventional inorganic fertilizers phosphate rock and triple superphosphate. The results show that many recycled P fertilizers (RPFs; e.g., digestates from urban organic wastes, biosolids and their ashes, meat and bone meal (MBM) and its recycling products) are competitive in terms of LCA results compared with conventional P fertilizers. For each of the P recycling sources, one or more treatment options were identified, which have more favorable LCA results than the conventional references. For sewage sludge, we found that direct application of the stabilized biosolids, and incineration with application of the ash showed the lowest LCA impacts per kg P; their treatments even generated net credits from added values. The same applies for the anaerobic digestion treatment of urban organic wastes. For MBM, low environmental impacts were identified for each of the analyzed treatment options, especially for anaerobic digestion, incineration, feeding with application of manure and direct application. Similarly, low environmental impacts and net credits were found for directly applied biomass ash. Some organically based RPFs demonstrate added values, i.e., as nitrogen and potassium fertilizer effect, energy gains during the treatment, or a humus sequestration potential. If these added values are considered in the LCAs, 11 out of 17 RPFs will have advantageous effects for the majority of addressed impact categories.

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