Modeling and assessment of dairy farm-based biogas plants in South Africa

Boadzo, A.; Chowdhury, S.

doi:10.1109/pes.2011.6039181

Cited by 4 publications

(1 citation statement)

References 6 publications

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“…The search of papers using the word combination described in the methodology, outputs 749 articles. By assessing the papers against the selection criteria, 30 articles ,− ,,− (4% of the initially found) are chosen. The main causes for the high rejection, according to criteria, are the following: First criteria: 84% of total output papers are not specific to the field and focus on codigestion, experimental measurements of methane yield, bacterial population, and/or different life-cycle-analysis indicator. Second criteria: 9% of the papers correspond to reviews and, therefore, are not primary sources. Third criteria: 7% of the articles are rejected because they report GHG emissions only for AD scenarios or baselines (i.e., not both scenarios). …”

Section: Resultsmentioning

confidence: 99%

Meta-Analysis of Greenhouse Gas Emissions from Anaerobic Digestion Processes in Dairy Farms

Miranda

Tuomisto

McCulloch

2015

Environ. Sci. Technol.

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This meta-analysis quantifies the changes in greenhouse gas (GHG) emissions from dairy farms, caused by anaerobically digesting (AD) cattle manure. As this is a novel quantifiable synthesis of the literature, a database of GHG emissions from dairy farms is created. Each case in the database consists of a baseline (reference with no AD system) and an AD scenario. To enable interstudy comparison, emissions are normalized by calculating relative changes (RCs). The distributions of RCs are reported by specific GHGs and operation units. Nonparametric tests are applied to the RCs in order to identify a statistical difference of AD with respect to baseline scenarios (Wilcoxon rank test), correlations (Spearman test), and best estimation for changes in emissions (Kernel density distribution estimator). From 749 studies identified, 30 papers yield 89 independent cases. The median reductions in emissions from the baseline scenarios, according to operation units, are -43.2% (n.s.) for storage, -6.3% for field application of slurries, -11.0% for offset of energy from fossil fuel, and +0.4% (n.s.) for offset of inorganic fertilizers. The leaks from digesters are found to significantly increase the emissions from baseline scenarios (median = +1.4%).

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Section: Resultsmentioning

confidence: 99%

Meta-Analysis of Greenhouse Gas Emissions from Anaerobic Digestion Processes in Dairy Farms

Miranda

Tuomisto

McCulloch

2015

Environ. Sci. Technol.

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What is the potential for biogas digesters to improve soil fertility and crop production in Sub-Saharan Africa?

Smith

Abegaz

Matthews

et al. 2014

Biomass and Bioenergy

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Three alternative soil amendments of organic wastes are considered: application of untreated animal manures, bioslurry from biogas digestion, composted materials, and biochar produced by pyrolysis cook-stoves. Application of untreated manures provides high input of available nutrients, which results in an initial flush in crop growth. However, risks of losing nutrients are high because manure is usually applied before sowing to avoid reduced yields due to phytotoxicity, resulting in increased losses by leaching or volatilization. Furthermore, the heterogeneous nature of untreated manures results in immobilization of nutrients by carbon-rich materials. A greater amount of nutrients are potentially available to crops from applied bioslurry. Typically 5-10% of the nitrogen is lost during anaerobic digestion, but bioslurry provides immediately available nutrients that can be applied as needed, so reducing risks of nutrient loss. If, however, bioslurry was applied in a single dose, losses would be similar in magnitude to untreated manures. Risks of nutrient losses are also lower when wastes are applied as composts, but in contrast to bioslurry, this is because the concentration of immediately available nutrients is very low, most nutrients being held in organic form that will become available only slowly over the growing season. Composts provide an option for single dose application, but a larger proportion of nitrogen is lost during composting (26-51%) than during anaerobic digestion (5-10%). Losses of nitrogen during pyrolysis are also very high (70-90%), but biochar can reduce losses of native soil nutrients by providing exchange sites that hold nutrients in the soil.

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