| 1. |
- Barta, Zsolt, et al.
(författare)
-
Effects of steam pretreatment and co-production with ethanol on the energy efficiency and process economics of combined biogas, heat and electricity production from industrial hemp
- 2013
-
Ingår i: Biotechnology for Biofuels. - : Springer Science and Business Media LLC. - 1754-6834. ; 6
-
Tidskriftsartikel (refereegranskat)abstract
- Background: The study presented here has used the commercial flow sheeting program Aspen Plus (TM) to evaluate techno-economic aspects of large-scale hemp-based processes for producing transportation fuels. The co-production of biogas, district heat and power from chopped and steam-pretreated hemp, and the co-production of ethanol, biogas, heat and power from steam-pretreated hemp were analysed. The analyses include assessments of heat demand, energy efficiency and process economics in terms of annual cash flows and minimum biogas and ethanol selling prices (MBSP and MESP). Results: Producing biogas, heat and power from chopped hemp has the highest overall energy efficiency, 84% of the theoretical maximum (based on lower heating values), providing that the maximum capacity of district heat is delivered. The combined production of ethanol, biogas, heat and power has the highest energy efficiency (49%) if district heat is not produced. Neither the inclusion of steam pretreatment nor co-production with ethanol has a large impact on the MBSP. Ethanol is more expensive to produce than biogas is, but this is compensated for by its higher market price. None of the scenarios examined are economically viable, since the MBSP (EUR 103-128 per MWh) is higher than the market price of biogas (EUR 67 per MWh). The largest contribution to the cost is the cost of feedstock. Decreasing the retention time in the biogas process for low solids streams by partly replacing continuous stirred tank reactors by high-rate bioreactors decreases the MBSP. Also, recycling part of the liquid from the effluent from anaerobic digestion decreases the MBSP. The production and prices of methane and ethanol influence the process economics more than the production and prices of electricity and district heat. Conclusions: To reduce the production cost of ethanol and biogas from biomass, the use of feedstocks that are cheaper than hemp, give higher output of ethanol and biogas, or combined production with higher value products are primarily suggested. Further, practical investigations on increased substrate concentration in biogas and ethanol production, recycling of the liquid in anaerobic digestion and separation of low solids flows into solid and a liquid fraction for improved reactor applications deserves further attention.
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
- Murto, Marika, et al.
(författare)
-
Evaluating the biogas potential of the dry fraction from pretreatment of food waste from households.
- 2013
-
Ingår i: Waste Management: international journal of integrated waste management, science and technology. - : Elsevier BV. - 1879-2456. ; 33:5, s. 1282-1289
-
Tidskriftsartikel (refereegranskat)abstract
- At the waste handling company NSR, Helsingborg, Sweden, the food waste fraction of source separated municipal solid waste is pretreated to obtain a liquid fraction, which is used for biogas production, and a dry fraction, which is at present incinerated. This pretreatment and separation is performed to remove impurities, however also some of the organic material is removed. The possibility of realising the methane potential of the dry fraction through batch-wise dry anaerobic digestion was investigated. The anaerobic digestion technique used was a two-stage process consisting of a static leach bed reactor and a methane reactor. Treatment of the dry fraction alone and in a mixture with structural material was tested to investigate the effect on the porosity of the leach bed. A tracer experiment was carried out to investigate the liquid flow through the leach beds, and this method proved useful in demonstrating a more homogenous flow through the leach bed when structural material was added. Addition of structural material to the dry fraction was needed to achieve a functional digestion process. A methane yield of 98m(3)/ton was obtained from the dry fraction mixed with structural material after 76days of digestion. This was in the same range as obtained in the laboratory scale biochemical methane potential test, showing that it was possible to extract the organic content in the dry fraction in this type of dry digestion system for the production of methane.
|
|
| 7. |
- Prade, Thomas, et al.
(författare)
-
EU sustainability criteria for biofuels potentially restrict ley crop production on marginal land for use as biogas substrate
- 2013
-
Ingår i: Grassland Science in Europe. ; 18, s. 528-530
-
Konferensbidrag (refereegranskat)abstract
- Ley crops can be grown to provide a substrate for biogas vehicle-fuel production on a range of soils including marginal land. According to EU regulations, such biofuel currently has to achieve an emission reduction of 35%, but tightened goals of 50 and 60% will come into effect as early as 2017. In two field trials (one on marginal soil, one on productive soil) ley crop mixtures were tested and the biomass DM yield was determined. In a life-cycle assessment approach, the emissions of the production chain for biogas-vehicle-fuel were estimated for a range of biomass DM yields. The results show that the emission intensity per energy unit of fuel produced is an asymptotic function of the DM yield. Currently, marginal lands not competing with food production can provide biofuels fulfilling the emission reduction requirements. However, a tightening of the goals to 50 or 60% is likely to cause a shift in biomass production towards better soils, potentially causing competition with food and feed production. Alternatively, the CO2 emissions from biomass production of marginal soils need to be further reduced, e.g. by increased nitrogen fixation or reduced machinery use.
|
|
| 8. |
|
|
