Enhancing anaerobic digestion of wheat straw through multistage milling

Abstract

The effects of a mechanical pretreatment, carried out by a two stages mill followed by fractionation into two different products, were determined on the biodegradability and methane yield of wheat straw. Straw was chopped in a knife mill to an average length of about 30 mm, and a portion was used as reference material. Pretreatment reduced the size of the processed straw, whose median particle size was 300μm and 1200μm for the fine and the coarse fractions, respectively. Untreated and pretreated materials were anaerobically digested in batch reactors under mesophilic conditions for 28 days. The methane yield of raw material was 167.8 Nm 3 tVS -1 , whereas the pretreated material reached an average methane yield of 250.6 Nm 3 tVS -1 , showing a 49.3 % gain on VS basis compared to the feedstock. The finest fraction of the processed material reached a methane production of 264.7 Nm 3 tVS -1 . The specific electric energy consumption was 66.6 kWh per ton of processed material. The energy efficiency was high, since consumption was only 23.7 % of the gross electric energy gain available after pretreatment. These results proved that the investigated pretreatment could be successfully implemented to improve methane production efficiency in anaerobic digesters.

Optimization of biogas yield from lignocellulosic materials with different pretreatment methods: a review

“…The table shows that there is no particular particle size of lignocellulose materials that is applicable for the optimum biogas yield of all the available feedstock. It can be observed that when the particle size of water hyacinth was reduced from 1.0 to 0.05 mm, the yield increased from 10 to 16% [ 107 ], whereas when wheat straw particle size was reduced from 1.2 to 0.3 mm, there was a decrease of 19.1 mL/g VS in the biogas yield [ 108 ]. It can also be inferred that at 0.3 mm particle size, different biomass produced different result.…”

“…It can also be inferred that at 0.3 mm particle size, different biomass produced different result. There was an increase of 4.6 mL/g Vs when rice straw was pretreated to 0.3 mm particle size [ 109 ], while the biogas yield was increased by 77.8 mL/g VS when wheat straw was pretreated to the same 0.3 mm particle size [ 108 ]. Likewise, it was shown that different mechanical pretreatment methods also have different effects on the same lignocellulose biomass.…”

“…Likewise, it was shown that different mechanical pretreatment methods also have different effects on the same lignocellulose biomass. Wheat straw was treated with two different mechanical methods of size reduction and high hydrostatic pressure, and the results indicated that the biogas yield was improved by 22.40% for size reduction [ 108 ], while the biogas yield from high hydrostatic pressure treatment was increased by 42.02% [ 110 ]. Although, this can still be research further with the use of the same bio-digester.…”

Insight into Pretreatment Methods of Lignocellulosic Biomass to Increase Biogas Yield: Current State, Challenges, and Opportunities

“…Likewise, barley straw presented an increase of 54% and 41% of methane yield at particle size of 5 mm and 20 mm, respectively [73]. It can also be observed that particle sizes larger and smaller than the range between 2 and 5 mm, presented a decrease in methane yield [68,73,74]. The observed variations on the effect of particle size, time, and speed of milling pointed out that apparently the best strategy for the mechanical pretreatment depends on the type the lignocellulosic material and a universal strategy cannot be recommended.…”

Enhancing and upgrading biogas and biomethane production in anaerobic digestion: a comprehensive review

“…Chemical pretreatment technique in terms of acid, alkali, oxidation and ozonolysis pretreatments has been reported to be a very effective technique for biogas/biomethane yield enhancement (Appels et al, 2011;Zhang et al, 2011;Biswas et al, 2014;Cesaro and Belgiorno, 2014;Ahring et al, 2015;Venturin et al, 2018;Antonopoulou et al, 2020;Dasgupta and Chandel, 2020;Lee et al, 2020). Physical pretreatment technique with respect to mechanical (milling), thermal (temperature-induced, steam explosion, liquid hot water), microwave irradiation, sonication and high-pressure homogenizer pretreatments have also been observed and reported to be moderately effective in the increase of biogas/biomethane yield (Hjorth et al, 2011;Pilarski et al, 2016;Dell'Omo and Froscia, 2018;Pengyu et al, 2017;M¨onch-Tegeder et al, 2014;Marañón et al, 2012;Bougrier et al, 2006;Ariunbaatar et al, 2014;Schwede et al, Frontiers in Energy Research frontiersin.org 13 2013;Menardo et al, 2012;Horn et al, 2011;Li et al, 2016;Lizasoain et al, 2017;Mulat et al, 2018;Steinbach et al, 2019;Weber et al, 2020;Passos and Ferrer, 2015;Qiao et al, 2013;Jiang et al, 2012;Panigrahi et al, 2019;Shang et al, 2019;Carrerre et al, 2016;Martin et al, 2013;Carrère et al, 2010;Ma et al, 2011). Table…”