Papers by Ylva Borgström
Linkopings Universitet har tillsammans med Poyry och Scandinavian Biogas Fuels drivit projektet ”... more Linkopings Universitet har tillsammans med Poyry och Scandinavian Biogas Fuels drivit projektet ”Etablering/effektivisering av biogasproduktion inom svensk pappers- och massaproduktion”. Potential ...
The methane potential of Swedish pulp and paper industry - A screening of wastewater effluents
The methane potential of Swedish pulp and paper industry - A screening of wastewater effluents
Applied Energy, 2013
With the final aim of reducing the energy consumption and increase the methane production at Swed... more With the final aim of reducing the energy consumption and increase the methane production at Swedish pulp and paper mills, the methane potential of 62 wastewater effluents from ten processes at seven pulp and/or paper mills (A-G) was determined in anaerobic batch digestion assays. This mapping is a first step towards an energy efficient and more sustainable utilization of the effluents by anaerobic digestion, and will be followed up by tests in lab-scale and pilot-scale reactors. Five of the mills produce kraft pulp (KP), one thermo-mechanical pulp (TMP), two chemical thermo-mechanical pulp (CTMP) and two neutral sulfite semichemical (NSSC) pulp. Both elemental and total chlorine free (ECF and TCF, respectively) bleaching processes were included. The effluents included material from wood rooms, cooking and oxygen delignification, bleaching (often both acid-and alkali effluents), drying and paper/board machinery as well as total effluents before and after sedimentation. The results from the screening showed a large variation in methane yields (percent of theoretical methane potential assuming 940 NmL CH 4 per g TOC) among the effluents. For the KP-mills, methane yields above 50% were obtained for the cooking effluents from mills D and F, paper machine wastewater from mill D, condensate streams from mills B, E and F and the composite pre-sedimentation effluent from mill D. The acidic ECF-effluents were shown to be the most toxic to the AD-flora and also seemed to have a negative effect on the yields of composite effluents downstream while three of the alkaline ECF-bleaching effluents gave positive methane yields. ECF bleaching streams gave higher methane yields when hardwood was processed. All TCF-bleaching effluents at the KP mills gave similar degradation patterns with final yields of 10-15% of the theoretical methane potential for four of the five effluents. The composite effluents from the two NSSC-processes gave methane yields of 60% of the theoretical potential. The TMP mill (A) gave the best average yield with all 6 effluents ranging 40-65% of the theoretical potential. The three samples from the CTMP process at mill B showed potentials around 40% while three of the six effluents at mill G (CTMP) yielded 45-50%.
The world needs new energy sources that are durable for long time and which not affect the enviro... more The world needs new energy sources that are durable for long time and which not affect the environment negatively. Biogas fulfills those demands. The biogas process is however not completely optimized. Several of the substrates used today for biogas production are slowly degraded and only partly digested in the process. Other substrates consist of unnecessarily much water which makes transportation costly. To optimize the process and make the biogas process more profitable, several pretreatment techniques are evaluated by direction of E.ON in this report: steam explosion, extrusion, lime treatment and dewatering. The hope is that one of those could increase the profitability and hopefully also enable substrates that not are working today like feathers and straw. To compare and evaluate the different pretreatment batch digester, experiments were carried out during 31-44 days for untreated and pretreated substrates. Most pretreated substrates were faster degraded than untreated and some also gave a higher methane yield. Chicken waste feathers and wheat straw, which had low methane yields untreated, were affected most by pretreatment. Steam exploded feathers gave after 44 days of digestion 141% higher methane yield and extruded straw gave 22% higher methane yield than untreated samples of the same substrate. A reference plant with a substrate mixture of 12500 tonnes of maize silage and 11500 tons of horsemanure annually was used to make economical calculations. Additionally, chicken waste feathers waste could be included. Obtainable for the reference plant were also chicken waste feathers. Steam explosion appeared to be too expensive for a plant in the size of the reference plant. Its large capacity could probably make it profitable for a much larger biogas plant running on a lot of hard digestible substrates. An extruder could be a profitable investment for the reference plant if the plant gets horse manure with straw as bedding material. To just use the extruder to pretreat maize silage could not make the investment profitable. Dewatering of manure gave significantly lower methane yield per dry weight but significantly higher methane yield per wet weight. The increase in methane yield per wet weight makes the substrate better for transportation. The dewatering equipment from Splitvision tried in this study had too high operational costs and was too expensive to make dewatering particularly profitable. Only when the farm was situated farther away than 40km from the biogas plant it was cheaper to dewater the manure before transport than to transport the manure without any pretreatment. Other dewatering equipments evaluated in this study had much lower operational costs and among those an equipment that makes dewatering profitable might therefore be found.
Methane potentials of the Swedish pulp and paper industry – A screening of wastewater effluents
Applied Energy, 2013
ABSTRACT With the final aim of reducing the energy consumption and increase the methane productio... more ABSTRACT With the final aim of reducing the energy consumption and increase the methane production at Swedish pulp and paper mills, the methane potential of 62 wastewater effluents from 10 processes at seven pulp and/or paper mills (A-G) was determined in anaerobic batch digestion assays. This mapping is a first step towards an energy efficient and more sustainable utilization of the effluents by anaerobic digestion, and will be followed up by tests in lab-scale and pilot-scale reactors. Five of the mills produce kraft pulp (KP), one thermo-mechanical pulp (TMP), two chemical thermo-mechanical pulp (CTMP) and two neutral sulfite semi-chemical (NSSC) pulp. Both elementary and total chlorine free (ECF and TCF, respectively) bleaching processes were included. The effluents included material from wood rooms, cooking and oxygen delignification, bleaching (often both acid- and alkali effluents), drying and paper/board machinery as well as total effluents before and after sedimentation. The results from the screening showed a large variation in methane yields (percent of theoretical methane potential assuming 940 NmL CH4 per g TOC) among the effluents. For the KP-mills, methane yields above 50% were obtained for the cooking effluents from mills D and F, paper machine wastewater from mill D, condensate streams from mills B, E and F and the composite pre-sedimentation effluent from mill D. The acidic ECF-effluents were shown to be the most toxic to the AD-flora and also seemed to have a negative effect on the yields of composite effluents downstream while three of the alkaline ECF-bleaching effluents gave positive methane yields. ECF bleaching streams gave higher methane yields when hardwood was processed. All TCF-bleaching effluents at the KP mills gave similar degradation patterns with final yields of 10-15% of the theoretical methane potential for four of the five effluents. The composite effluents from the two NSSC-processes gave methane yields of 60% of the theoretical potential. The TMP mill (A) gave the best average yield with all six effluents ranging 40-65% of the theoretical potential. The three samples from the CTMP process at mill B showed potentials around 40% while three of the six effluents at mill G (CTMP) yielded 45-50%.
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Papers by Ylva Borgström