Sven-Erik Svensson

Bioconversion of industrial hemp to ethanol and methane: The benefits of steam pretreatment and co-production

Several scenarios for ethanol production, methane production (by anaerobic digestion) and co-production of these, using autumn harvested hemp as substrate, were investigated and compared in terms of gross energy output. Steam pretreatment improved the methane production rate compared with mechanical grinding. The methane yield of steam pretreated stems was similar both with and without pre-hydrolysis with cellulolytic enzymes. Co-production of ethanol and methane from steam pretreated stems gave a high yield of transportation fuel, 11.1-11.7 MJ/kg processed stem dry matter (DM); more than twice that of ethanol production alone from hexoses, 4.4-5.1 MJ/kg processed stem DM. Co-production from the whole hemp plant would give 2600-3000 L ethanol and 2800-2900 m(3) methane, in total 171-180 GJ per 10,000 m(2) of agricultural land, based on a biomass yield of 16 Mg DM. Of this, the yeast and enzymes from ethanol production were estimated to contribute 700 m(3) (27 GJ) of methane.

Nutrient and cost optimization of fertilizing strategies for Salix including use of organic waste products

Abstract A model was developed to minimize the grower’s costs for fertilization of Salix aimed for energy production, when a user-defined amount of organic waste products and commercial fertilizers are available. The fertilizers applied have to fulfil the nutrient demand of the crop, while the regulations on maximum heavy metal loading rates must not be exceeded. The model described is based on mixed integer programming (MIP) and calculates the optimal amount of fertilizing products to apply in each year of a four year cutting cycle. The model is general and may be used for optimization of fertilization strategies for energy crops under a wide range of circumstances. Optimal fertilizing strategies were also studied for some typical cases in order to define the characteristics of the method and to study some general trends in the results. The results showed that the use of untreated municipal waste water was very economically favourable for fertilization of Salix in cases where this product is available and where conditions are suitable for a permanent irrigation system. Another important conclusion was that the nutrient demand of the Salix crop may be met by organic products, without exceeding the Swedish limits for maximum heavy metal application rates on agricultural land. A third conclusion was that products with low concentrations of nutrients, for example biogas sludge, are economically favourable for the grower when the transport distances are short. When the transport distances increase, more concentrated products such as commercial fertilizers become more competitive.

Ethanol production from industrial hemp: effect of combined dilute acid/steam pretreatment and economic aspects.

In the present study, combined steam (140-180°C) and dilute-acid pre-hydrolysis (0.0-2.0%) were applied to industrial hemp (Cannabis sativa L.), as pretreatment for lignocellulosic bioethanol production. The influence of the pretreatment conditions and cultivation type on the hydrolysis and ethanol yields was also evaluated. Pretreatment with 1% sulfuric acid at 180°C resulted in the highest glucose yield (73-74%) and ethanol yield of 75-79% (0.38-0.40 g-ethanol/g-glucose). Taking into account the costs of biomass processing, from field to ethanol facility storage, the field-dried hemp pretreated at the optimal conditions showed positive economic results. The type of hemp cultivation (organic or conventional) did not influence significantly the effectiveness of the pretreatment as well as subsequent enzymatic hydrolysis and ethanol fermentation.

Perennial species mixtures for multifunctional production of biomass on marginal land

Multifunctional agriculture provides noncommodity functions and services along with food, feed and bioenergy feedstocks, for example by preserving or promoting biodiversity, improving soil fertility, mitigating climate change and environmental degradation, and contributing to the socio‐economic viability of rural areas. Producing biomass for bioenergy from low‐input perennial species mixtures on marginal land has the potential to support biodiversity and soil carbon sequestration in synergy with greenhouse gas mitigation. We compared biomass production in species‐rich mixtures of perennial grasses, legumes and forbs with pure‐stand grasses and relatively species‐poor mixtures under different nitrogen fertilization regimes. Field experiments were performed on different types of marginal land, that is agricultural field margins and land with poor soil fertility, at four sites in southernmost and western Sweden. Biomass production was measured for three years in perennial grasses grown as pure stands, in legume‐grass mixtures, and legume‐grass‐forb mixtures across a species richness gradient. In unfertilized species‐rich mixtures, average biomass yields per experimental site and year were in the range from 3 to 9 metric ton DM ha−1 yr−1. While the most productive pure‐stand grasses fertilized with 60–120 kg N ha−1 yr−1 often produced higher biomass yields than unfertilized mixtures, these differences were generally smaller than the variations between years and sites. Calculations of climate impact using the harvested biomass for conversion to biogas as vehicle fuel showed that the average greenhouse gas emissions per energy unit were about 50% lower in unfertilized systems than in treatments fertilized with 100–120 kg N ha−1 yr−1. Our findings thereby show that unfertilized species‐rich perennial plant mixtures on marginal land provide resource‐efficient biomass production and contribute to the mitigation of climate change. Perennial species mixtures managed with low inputs thus promote synergies between productivity and biodiversity in the perspective of climate‐smart and multifunctional biomass production.

Economically Viable Components from Jerusalem Artichoke (Helianthus tuberosus L.) in a Biorefinery Concept.

Biorefinery applications are receiving growing interest due to climatic and waste disposal issues and lack of petroleum resources. Jerusalem artichoke (Helianthus tuberosus L.) is suitable for biorefinery applications due to high biomass production and limited cultivation requirements. This paper focuses on the potential of Jerusalem artichoke as a biorefinery crop and the most viable products in such a case. The carbohydrates in the tubers were found to have potential for production of platform chemicals, e.g., succinic acid. However, economic analysis showed that production of platform chemicals as a single product was too expensive to be competitive with petrochemically produced sugars. Therefore, production of several products from the same crop is a must. Additional products are protein based ones from tubers and leaves and biogas from residues, although both are of low value and amount. High bioactive activity was found in the young leaves of the crop, and the sesquiterpene lactones are of specific interest, as other compounds from this group have shown inhibitory effects on several human diseases. Thus, future focus should be on understanding the usefulness of small molecules, to develop methods for their extraction and purification and to further develop sustainable and viable methods for the production of platform chemicals.

Ammonia sanitization of blackwater for safe use as fertilizer

Source-separated blackwater from low-flush toilets contains plant-available nutrients and can be used as a fertilizer. The aim of the study was to evaluate the impact on pathogen inactivation when treating blackwater with urea and/or lime. Blackwater was spiked with Salmonella typhimurium, Escherichia coli O157, Enterococcus faecalis, and Ascaris suum eggs, and treated with urea and/or lime in concentrations up to 0.1% w/w. The bottles were kept in a storage facility (manure slurry tank) for 102 days while monitoring the pathogen concentrations. The treatment time needed to meet the requirement for Salmonella and E. coli reduction could be reduced at least six-fold. The enterococci were more persistent, and only the highest treatment doses had a significantly higher inactivation than the controls. The Ascaris egg viability was only reduced by around 50%, so higher urea/lime doses and/or longer treatment times are required to fulfill the treatment requirements of 3 log10 reductions of parasite eggs.