Abstract
This paper presents the topic of the management of livestock effluents and, therefore, nutrients (particularly N) in the framework of the biogas supply chain. The bio-refinery will be analyzed as a unique system, from the farm to the biomass produced and sent to anaerobic digestion, focusing on the fate/change of the flow of material and nutrients content through the system. Within four categories of farms considered in the article, integrated ones frequently have a breeding consistency from 90 to 320 heads, according to more extensive or intensive settings. These farms must manage from 3.62 to 12.81 m3 day−1 of slurry and from 11.40 to 40.34 kg day−1 of nitrogen (N) as the sum of excreta from all herd categories. By selecting a hypo-protein diet, a reduction of 10% and 24% for total effluent amount and for N excreted, respectively, can be achieved. Nitrogen can be reduced up to 45% if the crude protein content is limited and a further 0.23% if animals of similar ages, weights and (or) production or management are grouped and fed according to specific requirements. Integrated farms can implement farming activity with biogas production, possibly adding agricultural residues to the anaerobically-digested biomass. Average biogas yields for cattle effluents range from 200 to 400 m3 ton−1 VS (volatile solids). Values from 320 to 672 m3 day−1 of biogas can be produced, obtaining average values from 26 to 54.5 kWe (kilowatt-electric). This type of farm can well balance farm-production profit, environmental protection, animal husbandry well-being and energy self-sufficiency.
Highlights
Following the concept of sustainable development as defined by the Brundtland Commission, energy systems should be ecologically, socially and economically sustainable, so that the present generation can meet its energy needs without compromising the ability of future generations to meet their energy and other needs [1]
Technique makes use of the whole plant, while first-generation biofuels only use the starchy and oleic parts of the feedstock [12,13]. These findings indicate in certain respects the environmental and economic advantageousness of biogas [14]
It is influenced by the setting of the stall and, in particular, by the feed supply, housing types and effluent management and storage on the farm
Summary
Following the concept of sustainable development as defined by the Brundtland Commission, energy systems should be ecologically, socially and economically sustainable, so that the present generation can meet its energy needs without compromising the ability of future generations to meet their energy and other needs [1]. Thereby, energy production via biomass could be regarded as a promising approach, which helps to preserve non-renewable resources, improves energy security, mitigates the greenhouse effect and promotes regional development [2,3,4]. Association) (2013) [5], bioenergy represented 68% of the total gross inland consumption of renewables in Europe in 2011. Use of renewable biomass (including energy crops and organic wastes) as an energy resource is “greener” with respect to most pollutants, but its use represents a closed balanced carbon cycle with respect to atmospheric carbon dioxide. Abbasi and Abbasi [7,8] give a rather isolated standing about biomass used for renewable energy A third concern is the recognized need for efficient methods for treatment and disposal of large quantities of municipal, industrial and agricultural organic wastes [6].
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