| 1. |
- Abubaker, Jamal, et al.
(författare)
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Biogas residues as fertilisers - Effects on wheat growth and soil microbial activities
- 2012
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Ingår i: Applied Energy. - : Elsevier BV. - 0306-2619 .- 1872-9118. ; 99, s. 126-134
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Tidskriftsartikel (refereegranskat)abstract
- Residues from the biogas process are a relatively new type of organic fertiliser with composition varying with origin of the raw material fed into the biogas process. The performance of four different biogas residues (BRs) was evaluated and compared with that of pig slurry (PS) and mineral fertiliser (NPK) in pots filled with sandy soil and fertilised at rates corresponding to 35,70 and 140 kg NH4+-N ha(-1). After sowing with spring wheat, the pots were incubated in a growth chamber. Total biomass yield and relative yields of ear, straw and root fractions were measured at harvest. Nitrogen mineralisation capacity (NMC) and potential ammonium oxidation rate (PAO) in soil were assessed. The fertilisation based on NH4+-N led to high addition of Tot C, Org N, Tot P, Tot K, Tot Mg and Zn at application of PS compared with BR. Biomass yields generally increased with increasing fertiliser rate but the response varied between the fertilisers. The BR yields compared well with NPK, but PS resulted in significantly higher yields. PS gave lower relative biomass of ears and higher relative biomass of roots compared with BR and NPK. The BR treatment yielding the lowest overall biomass also produced plants with the lowest relative root biomass, but partly compensated for this by increasing the relative ear biomass with increasing fertiliser rate. The NMC and PAO in soil had increased by the end of the experiment in almost all treatments. The high NMC in the PS treatment resulted in calculated mineralised N corresponding to 50-82 kg ha(-1) during the experimental period. In conclusion, fertilisation with biogas residues gave similar biomass yields but increased NMC and PAO in soil compared with NPK. Pig slurry gave the overall highest yields and NMC, but a PAO comparable to most BR. (C) 2012 Elsevier Ltd. All rights reserved.
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| 2. |
- Abubaker, Jamal, et al.
(författare)
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Short-Term Effects of Biogas Digestates and Pig Slurry Application on Soil Microbial Activity
- 2015
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Ingår i: Applied and Environmental Soil Science. - : Hindawi Limited. - 1687-7667 .- 1687-7675. ; 2015, s. 1-15
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Tidskriftsartikel (refereegranskat)abstract
- The effect of four biogas digestates (BD-A, BD-B, BD-C, and BD-D) and pig slurry (PS) on soil microbial functions was assessed at application rates corresponding to 0–1120 kg-N ha−1. At dose corresponding to 140 kg-N ha−1, 30.9–32.5% of the carbon applied in BD-A, BD-C, and PS was utilized during 12 days, while for BD-B and BD-D corresponding utilization was 19.0 and 16.9%, respectively. All BDs resulted in net nitrogen assimilation at low rates (17.5–140 kg-N ha−1) but net mineralization dominated at higher rates. PS resulted in net mineralization at all application rates. All residues inhibited potential ammonium oxidation (PAO), with EC50-values ranging between 45 and 302 kg-N ha−1. Low rates of BDs appeared to weakly stimulate potential denitrification activity (PDA), while higher rates resulted in logarithmic decrease. The EC50-values for PDA were between 238 and 347 kg-N ha−1. No inhibition of PDA was observed after amendment with PS. In conclusion, biogas digestates inhibited ammonia oxidation and denitrification, which could be an early warning of potential hazardous substances in the digestates. However, this effect can also be regarded as positive, since it may reduce nitrogen losses.
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| 3. |
- Risberg, Kajsa, et al.
(författare)
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Biogas production from wheat straw and manure : Impact of pretreatment and process operating parameters
- 2013
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Ingår i: Bioresource Technology. - : Elsevier BV. - 0960-8524 .- 1873-2976. ; 149, s. 232-237
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Tidskriftsartikel (refereegranskat)abstract
- Non-treated or steam-exploded straw in co-digestion with cattle manure was evaluated as a substrate for biogas production compared with manure as the sole substrate. All digestions were performed in laboratory-scale CSTR reactors (5L) operating with an organic loading late of approximately 2.8g VS/L/day, independent of substrate mixture. The hydraulic retention was 25days and an operating temperature of 37, 44 or 52°C. The co-digestion with steam exploded straw and manure was evaluated with two different mixtures, with different proportion. The results showed stable performance but low methane yields (0.13-0.21NLCH4/kg VS) for both manure alone and in co-digestion with the straw. Straw appeared to give similar yield as manure and steam-explosion treatment of the straw did not increase gas yields. Furthermore, there were only slight differences at the different operating temperatures.
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| 4. |
- Risberg, Kajsa, et al.
(författare)
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Comparative characterization of digestate versus pig slurry and cow manure - Chemical composition and effects on soil microbial activity
- 2017
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Ingår i: Waste Management. - : Elsevier BV. - 0956-053X .- 1879-2456. ; 61, s. 529-538
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Tidskriftsartikel (refereegranskat)abstract
- The growing number of biogas plants in Europe has resulted in increased production of nutrient-rich digestate with great potential as fertilizer for arable land. The nutrient composition of digestate varies with the substrate treated in the biogas plant and may contain compounds that stimulate or inhibit soil microbial activity. This study compared 20 digestates (D) with 10 pig slurries (PS) and 10 cow manures (CM) regarding their chemical content and their effect on soil microbial activities, i.e. potential ammonia oxidation rate (PAO) and soil respiration. The results showed no significant differences within the D group when divided based on substrate type. i.e. manure dominated vs. other organic waste materials in any of the tests. In general D contained significantly higher concentrations of ammonium while the concentrations of total carbon and volatile fatty acids were higher in PS and CM than in D. The D showed both stimulating and inhibiting effects on PAO, while all CM and all PS except one showed inhibiting effects on PAO. However, PAO activity was negatively correlated with the content of volatile fatty acids in the residues indicating that these compounds may be the cause of the inhibition. The maximum respiration activity (hpeakmax) was lower and the time point for the maximum respiration activity (t(peakmax))occurred earlier for D compared with CM and PS. This earlier peak time could be indicative of a high proportion of easily degradable carbon in D compared with PS and CM. However, the utilization rate of carbon, i.e. the proportion of added organic C converted to CO2-C during 12 days, did not differ significantly between D, PS and CM, indicating that overall carbon quality in the different fertilizers was still roughly comparable. In short, our results suggest that digestates were different compared with PS and CM but without posing a higher risk with respect to their impact on soil microbial activity. (C) 2016 The Author(s). Published by Elsevier Ltd.
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| 5. |
- Risberg, Kajsa
(författare)
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Quality and function of anaerobic digestion residues
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The growing number of biogas plants in Europe has resulted in increased production of nutrient-rich digestate, which has potential as fertiliser on arable land. Many different organic materials can be degraded in the anaerobic digestion process, with most macronutrients and micronutrients retained in the digestate. Depending on the ingoing organic substrate and management of the biogas process, the nutrient content of digestate varies widely. It can also contain compounds such as heavy metals and organic pollutants that are potentially toxic to soil microorganisms. Previous studies on the effect of digestate on soil microorganisms and crop yield have yielded contradictory results, so further investigations are needed to determine its true fertiliser value. In this thesis, the fertiliser effect of different types of digestate originating from biogas plants operating with various substrates and operating parameters was determined by measuring: 1) general and specific soil microbial activity, 2) bacterial and archaeal community composition, 3) crop growth and 4) chemical and physical composition of different digestates. Soil respiration generally displayed a positive response to digestate addition, but soil respiration curves revealed differences in quality and quantity of organic carbon between digestate, pig slurry and cow manure. However, the total utilisation rate of the organic carbon in digestate, pig slurry and cow manure did not differ. Moreover, digestate showed both stimulatory and inhibitory effects on potential ammonia oxidation, while pig slurry and cow manure had a more consistent inhibitory effect. Addition of digestate to soil resulted in increased wheat yield compared with control soil and mineral fertiliser, but final yield was not as high as that from pig slurry. Digestate was also generally characterised by a higher content of ammonium and lower content of organic carbon than pig slurry and cow manure. Addition of digestate to soil resulted in changes in the microbial community structure, with less pronounced effect in sandy soils, but no change in diversity was detected. It can be concluded that the digestate from biogas plants has great potential as a fertiliser in crop production and does not seem to pose a greater risk of disturbing soil microorganisms than pig slurry and cow manure when spread on arable land.
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