| 1. |
- Gissén, Charlott, et al.
(författare)
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Comparing energy crops for biogas production Yields, energy input and costs in cultivation using digestate and mineral fertilisation
- 2014
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Ingår i: Biomass & Bioenergy. - : Elsevier BV. - 1873-2909 .- 0961-9534. ; 64, s. 199-210
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Tidskriftsartikel (refereegranskat)abstract
- Analyses of six crops grown in southern Sweden for biogas production (hemp, sugar beet, maize, triticale, grass/clover ley, winter wheat) showed varying performance regarding methane yield per hectare and energy input and costs in the production and supply of crops as biogas feedstock. The highest biomass and biogas yield was observed for sugar beet. Crops with lower risk of negative environmental impact in cultivation, such as ley and hemp, produced less than half the methane energy yield per hectare. Triticale, also having less risk of negative environmental impact, gave an energy yield similar to that of winter wheat grain and maize. Replacing most of the mineral fertiliser with biogas digestate did not, with the exception for hemp, influence crop yields per hectare, but energy input in cultivation decreased by on average 34% for the six crops tested. For hemp and sugar beet the biogas feedstock costs for the freshly harvested crop per GJ methane were close to that of the economic reference crop, winter wheat grain. For maize, beet tops and first and second year ley, the feedstock costs were lower, and for triticale much lower. When ensiled crops were used for biogas the feedstock costs increased and only those of triticale silage remained slightly lower than the cost of dried wheat grain. However, all feedstock costs were so high that profitable biogas production based solely on ensiled crops would be difficult to achieve at present Swedish biogas sales prices. (c) 2014 Elsevier Ltd. All rights reserved.
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| 2. |
- Ivo Achu, Nges, et al.
(författare)
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Benefits of supplementing an industrial waste anaerobic digester with energy crops for increased biogas production.
- 2012
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Ingår i: Waste Management: international journal of integrated waste management, science and technology. - : Elsevier BV. - 1879-2456. ; 32:1, s. 53-59
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Tidskriftsartikel (refereegranskat)abstract
- Currently, there is increasing competition for waste as feedstock for the growing number of biogas plants. This has led to fluctuation in feedstock supply and biogas plants being operated below maximum capacity. The feasibility of supplementing a protein/lipid-rich industrial waste (pig manure, slaughterhouse waste, food processing and poultry waste) mesophilic anaerobic digester with carbohydrate-rich energy crops (hemp, maize and triticale) was therefore studied in laboratory scale batch and continuous stirred tank reactors (CSTR) with a view to scale-up to a commercial biogas process. Co-digesting industrial waste and crops led to significant improvement in methane yield per ton of feedstock and carbon-to-nitrogen ratio as compared to digestion of the industrial waste alone. Biogas production from crops in combination with industrial waste also avoids the need for micronutrients normally required in crop digestion. The batch co-digestion methane yields were used to predict co-digestion methane yield in full scale operation. This was done based on the ratio of methane yields observed for laboratory batch and CSTR experiments compared to full scale CSTR digestion of industrial waste. The economy of crop-based biogas production is limited under Swedish conditions; therefore, adding crops to existing industrial waste digestion could be a viable alternative to ensure a constant/reliable supply of feedstock to the anaerobic digester.
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| 3. |
- Ivo Achu, Nges, et al.
(författare)
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High methane yields and stable operation during anaerobic digestion of nutrient-supplemented energy crop mixtures
- 2012
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Ingår i: Biomass & Bioenergy. - : Elsevier BV. - 1873-2909 .- 0961-9534. ; 47, s. 62-70
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Tidskriftsartikel (refereegranskat)abstract
- The feasibility of digesting energy crops supplemented with macro- and micronutrients instead of manure, without the commonly applied long hydraulic retention time (HRT), was investigated in long-term, single-stage continuous stirred tank processes. The crops used were mixtures of sugar beets, maize and whole crop triticale. The organic loading rate (OLR) measured as a total solid (TS) was 1.5-5.5 kg m(-3) d(-1) and the HRT from 30 to 40 days. The results showed high methane yields, comparable to those in batch digestion, and high stability. The digestion of beets only was most stable, and showed the highest average TS-based methane yield (383 +/- 26 m(3) kg(-1)) at an OLR of 4.5 kg m(-3) d(-1) and a HRT of 40 days. No significant difference in methane yield was found for all the crop mixtures during stable operation. Nutrient addition therefore showed the same stimulatory and stabilising effects as manure with high methane yields achieved at relatively short HRTs. (c) 2012 Elsevier Ltd. All rights reserved.
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| 4. |
- Ivo Achu, Nges, et al.
(författare)
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Improved utilization of fish waste by anaerobic digestion following omega-3 fatty acids extraction.
- 2012
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Ingår i: Journal of Environmental Management. - : Elsevier BV. - 0301-4797. ; 110, s. 159-165
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Tidskriftsartikel (refereegranskat)abstract
- Fish waste is a potentially valuable resource from which high-value products can be obtained. Anaerobic digestion of the original fish waste and the fish sludge remaining after enzymatic pre-treatment to extract fish oil and fish protein hydrolysate was evaluated regarding the potential for methane production. The results showed high biodegradability of both fish sludge and fish waste, giving specific methane yields of 742 and 828 m(3)CH(4)/tons VS added, respectively. However, chemical analysis showed high concentrations of light metals which, together with high fat and protein contents, could be inhibitory to methanogenic bacteria. The feasibility of co-digesting the fish sludge with a carbohydrate-rich residue from crop production was thus investigated, and a full-scale process outlined for converting odorous fish waste to useful products.
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| 5. |
- Ivo Achu, Nges, et al.
(författare)
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Stable operation during pilot-scale anaerobic digestion of nutrient-supplemented maize/sugar beet silage
- 2012
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Ingår i: Bioresource Technology. - : Elsevier. - 0960-8524 .- 1873-2976. ; 118, s. 445-454
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Tidskriftsartikel (refereegranskat)abstract
- Biogas production from maize/sugar beet silage was studied under mesophilic conditions in a continuous stirred tank reactor pilot-scale process. While energy crop mono-digestion is often performed with very long hydraulic retention times (HRTs), the present study demonstrated an efficient process operating with a 50-day HRT and a corrected total solids (TScorr) based organic loading rate of 3.4 kg/m3×d. The good performance was attributed to supplementation with both macro- and micronutrients and was evidenced by good methane yields (318 m3/ton TScorr) which were comparable to laboratory maximum expected yields plus low total volatile fatty acid concentrations (< 0.8 g/L). A viscoplastic and thixotropic digester fluid behaviour was observed, and the viscosity problems common in crop mono-digestion were not seen in this study. The effluent also complied with Swedish certification standards for bio-fertilizer for farmland application. Nutrient addition thus rendered a stable biogas process, while the effluent was a good quality bio-fertilizer.
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| 6. |
- Kreuger, Emma, et al.
(författare)
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Ensiling of crops for biogas production: effects on methane yield and total solids determination
- 2011
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Ingår i: Biotechnology for Biofuels. - : Springer Science and Business Media LLC. - 1754-6834. ; 4
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Tidskriftsartikel (refereegranskat)abstract
- Background: Ensiling is a common method of preserving energy crops for anaerobic digestion, and many scientific studies report that ensiling increases the methane yield. In this study, the ensiling process and the methane yields before and after ensiling were studied for four crop materials. Results: The changes in wet weight and total solids (TS) during ensiling were small and the loss of energy negligible. The methane yields related to wet weight and to volatile solids (VS) were not significantly different before and after ensiling when the VS were corrected for loss of volatile compounds during TS and VS determination. However, when the TS were measured according to standard methods and not corrected for losses of volatile compounds, the TS loss during ensiling was overestimated for maize and sugar beet. The same methodological error leads to overestimation of methane yields; when TS and VS were not corrected the methane yield appeared to be 51% higher for ensiled than fresh sugar beet. Conclusions: Ensiling did not increase the methane yield of the studied crops. Published methane yields, as well as other information on silage related to uncorrected amounts of TS and VS, should be regarded with caution.
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