Linn Solli
Research Scientist
Biography
Education: Doctoral degree (PhD) (2017) in microbiology at the University of Life Sciences, NMBU.
Area of research:
- Blue / green bio economy (agriculture / aquaculture)
- Climate and environmentally friendly management of organic residual fractions (animal manure, fish sludge, slaughterhouse waste etc)
- Anaerobic degradation of organic fractions
- Biogas process and methane production
- Dynamics in anaerobic microbiological communities
- Tolerance for nitrogen (ammonia) and fatty acids (LCFA / VFA) in anaerobic microbiological communities
- Syntrophic relations between different groups of bacteria and methanogenic Archaea
At Ås we have Norway's largest biogas laboratory, with equipment and instruments for various types of biogas experiments (e.g. potential tests, long-term continuous biogas experiments, analysis of gas and organic material). The laboratory also has facilities for micro-algae experiments, composting experiments and a number of different analyzes.
Abstract
Since the 1950s, the use of plastics in agriculture has helped solving many challenges related to food production, while its persistence and mismanagement has led to the plastic pollution we face today. Soils are no exception and concentrations of polyethylene mulch debris up to 380 kg/ha have been reported in Chinese agricultural soils. A variety of biodegradable plastic products have thus been developed and marketed, with the aim to solve plastic pollution through complete degradation after use. But the environmental conditions for rapid and complete degradation are not always fulfilled, and the risk that biodegradable plastics could also contribute to plastic pollution must be evaluated. In this presentation, we want to share the knowledge gained through research projects on biodegradable plastics in agricultural soil, where we both studied the degradation of biodegradable mulch under Nordic soil conditions, and the fate of other biodegradable plastics in soil amendments such as compost and biogas digestate. A two-year field experiment with biodegradable mulch (PBAT-starch and PBAT-PLA) buried in soil in mesh bags showed that also under colder climatic conditions does degradation occur, involving fragmentation already after 2 months, but that complete degradation may take 3 to 9 years, depending on soil temperature and soil organic matter content (both correlate positively with degradation rate). Accumulation is therefore likely to happen when biodegradable mulch is repeatedly used every year. A full-scale experiment with compostable plastic cups (PLA) at an industrial composting plant, where we followed their fate and conducted metagenomic analysis over 13 weeks, demonstrated the major role played by fungi for a successful degradation of PLA. However, the successful management of biodegradable plastic products largely depends on existing waste management infrastructure. Most biodegradable plastic bags, labelled as compostable and used for food waste collection do not end up in industrial composting plants in Norway, but in biogas production plants. Here, we showed that these plastic bags (Mater-Bi®) are only marginally degraded (maximum 21-33 % mass loss) during biogas production, and likely to end up in biogas digestate and then in agricultural soils, unless digestate is treated to remove plastic residues.
Abstract
Birch wood is a potential feedstock for biogas production in Northern Europe; however, the lignocellulosic matrix is recalcitrant preventing efficient conversion to methane. To improve digestibility, birch wood was thermally pre-treated using steam explosion at 220 °C for 10 min. The steam-exploded birch wood (SEBW) was co-digested with cow manure for a period of 120 days in continuously fed CSTRs where the microbial community adapted to the SEBW feedstock. Changes in the microbial community were tracked by stable carbon isotopes- and 16S r RNA analyses. The results showed that the adapted microbial culture could increase methane production up to 365 mL/g VS day, which is higher than previously reported methane production from pre-treated SEBW. This study also revealed that the microbial adaptation significantly increased the tolerance of the microbial community against the inhibitors furfural and HMF which were formed during pre-treatment of birch. The results of the microbial analysis indicated that the relative amount of cellulosic hydrolytic microorganisms (e.g. Actinobacteriota and Fibrobacterota) increased and replaced syntrophic acetate bacteria (e.g. Cloacimonadota, Dethiobacteraceae, and Syntrophomonadaceae) as a function of time. Moreover, the stable carbon isotope analysis indicated that the acetoclastic pathway became the main route for methane production after long-term adaptation. The shift in methane production pathway and change in microbial community shows that for anaerobic digestion of SEBW, the hydrolysis step is important. Although acetoclastic methanogens became dominant after 120 days, a potential route for methane production could also be a direct electron transfer among Sedimentibacter and methanogen archaea.
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Answers to survey asking for suggestions for new products in EU's new regulation for fertilisers. Fish sludge is suggested as material in compost and digestate, and a summary with references is provided.
Authors
Seyedbehnam Hashemi Linn Solli Roald Aasen Jacob Joseph Lamb Svein Jarle Horn Kristian Myklebust LienAbstract
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Four lab scale biogas reactors fed with a substrate composition of ensiled fish waste and manure fixed at 13 and 87 vol %, respectively, were operated with HRTs of 20, 25, 30 and 40 days. Biogas process performance and stability were evaluated with regard to CH4 yields, NH4+ accumulation and abundance of NH4+-tolerant microorganisms. Process performance in the reactors operated at different HRTs were compared to process performance in reactors operated with constant HRT, fed with increased ratios of fish waste. The process performance and microbial dynamics were stable in reactors operated at constant amount of fish waste in the feed and with different HRTs. In the reactors added elevated ratios of fish waste, the concentration of NH4+ and abundance of NH4+-tolerant acetate oxidizing bacteria increased. The biogas process failed in these reactors simultaneously with an observed shift in microbial composition. In particular, the bacterium Tepidanaerobacter Acetatoxydans seemed to affect the biogas process stability. The hydrogenotrophic Methanomicrobiales increased in abundance in response to higher fish waste loading and NH4+ concentrations. This study showed that at a loading of 13% fish waste, it is possible to decrease the HRT from 30 to 20 days without markedly inhibiting the process stability.
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Linn SolliAbstract
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John Christian Gaby Espen Govasmark Live Heldal Hagen Lisa Paruch Linn Solli Phillip Pope Svein Jarle HornAbstract
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John Christian Gaby Espen Govasmark Live Heldal Hagen Lisa Paruch Linn Solli Magnus Øverlie Arntzen Phillip Pope Svein Jarle HornAbstract
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John Christian Gaby Jeremy Frank Espen Govasmark Live Heldal Hagen Lisa Paruch Linn Solli Phillip Pope Svein Jarle HornAbstract
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John Christian Gaby Jeremy Frank Espen Govasmark Live Heldal Hagen Lisa Paruch Linn Solli Phillip Pope Svein Jarle HornAbstract
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Linn SolliAbstract
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Linn SolliAbstract
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