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Improving methane production from wheat straw by digestate liquor recirculation in continuous stirred tank processes

Peng, Xiaowei LU ; Ivo Achu, Nges LU and Liu, Jing LU (2016) In Renewable Energy 85. p.12-18
Abstract
Wheat straw is an abundant, cheap substrate that can be used for methane production. However, the nutrient content in straw is inadequate for methane fermentation. In this study, recycling digestate liquor was implemented in single-stage continuous stirred tank processes for enrichment of the nutrient content of straw with the aim of improving the methane production. The VS-based organic loading rate was set at 2 g/(L d) and the solid retention time at 40 days. When wheat straw alone was used as the substrate, the methane yields achieved with digestate liquor recycling was on average 240 ml CH4/g VS giving a 21% improvement over the processes without recycling. However, over time, the processes suffered from declining methane yields and... (More)
Wheat straw is an abundant, cheap substrate that can be used for methane production. However, the nutrient content in straw is inadequate for methane fermentation. In this study, recycling digestate liquor was implemented in single-stage continuous stirred tank processes for enrichment of the nutrient content of straw with the aim of improving the methane production. The VS-based organic loading rate was set at 2 g/(L d) and the solid retention time at 40 days. When wheat straw alone was used as the substrate, the methane yields achieved with digestate liquor recycling was on average 240 ml CH4/g VS giving a 21% improvement over the processes without recycling. However, over time, the processes suffered from declining methane yields and poor stability evidenced by low pH. To maintain process stability, wheat straw was co-digested with sewage sludge or supplemented with macronutrients (nitrogen and phosphorous). As a result, the processes with digestate liquor recycling could be operated stably, achieving methane yields ranging from 288 to 296 ml CH4/g VS. Besides, the processes could not be operated sturdily with supplementation of macronutrients without digestate liquor recycling. The highest methane yield (296 16 ml CH4/g VS) was achieved by co-digestion with sewage sludge plus recycling of digestate liquor after filtration (retention of nutrients and microorganisms). This was comparable to the maximum expected methane yield of 293 13 ml CH4/g VS achieved in batch test. The present study therefore demonstrated that digestate liquor recycling could lead to a decreased dilution of vital nutrients from the reactors thereby rendering high process performance and stability. (C) 2015 Elsevier Ltd. All rights reserved. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
straw, Wheat, Sewage sludge, Macronutrients, Digestate, Anaerobic digestion
in
Renewable Energy
volume
85
pages
12 - 18
publisher
Elsevier
external identifiers
  • wos:000363344800002
  • scopus:84937622535
ISSN
0960-1481
DOI
10.1016/j.renene.2015.06.023
language
English
LU publication?
yes
id
51a8a10e-7be8-4eb8-86c9-13287e8afd83 (old id 8195156)
date added to LUP
2015-11-26 09:15:50
date last changed
2017-11-12 03:03:11
@article{51a8a10e-7be8-4eb8-86c9-13287e8afd83,
  abstract     = {Wheat straw is an abundant, cheap substrate that can be used for methane production. However, the nutrient content in straw is inadequate for methane fermentation. In this study, recycling digestate liquor was implemented in single-stage continuous stirred tank processes for enrichment of the nutrient content of straw with the aim of improving the methane production. The VS-based organic loading rate was set at 2 g/(L d) and the solid retention time at 40 days. When wheat straw alone was used as the substrate, the methane yields achieved with digestate liquor recycling was on average 240 ml CH4/g VS giving a 21% improvement over the processes without recycling. However, over time, the processes suffered from declining methane yields and poor stability evidenced by low pH. To maintain process stability, wheat straw was co-digested with sewage sludge or supplemented with macronutrients (nitrogen and phosphorous). As a result, the processes with digestate liquor recycling could be operated stably, achieving methane yields ranging from 288 to 296 ml CH4/g VS. Besides, the processes could not be operated sturdily with supplementation of macronutrients without digestate liquor recycling. The highest methane yield (296 16 ml CH4/g VS) was achieved by co-digestion with sewage sludge plus recycling of digestate liquor after filtration (retention of nutrients and microorganisms). This was comparable to the maximum expected methane yield of 293 13 ml CH4/g VS achieved in batch test. The present study therefore demonstrated that digestate liquor recycling could lead to a decreased dilution of vital nutrients from the reactors thereby rendering high process performance and stability. (C) 2015 Elsevier Ltd. All rights reserved.},
  author       = {Peng, Xiaowei and Ivo Achu, Nges and Liu, Jing},
  issn         = {0960-1481},
  keyword      = {straw,Wheat,Sewage sludge,Macronutrients,Digestate,Anaerobic digestion},
  language     = {eng},
  pages        = {12--18},
  publisher    = {Elsevier},
  series       = {Renewable Energy},
  title        = {Improving methane production from wheat straw by digestate liquor recirculation in continuous stirred tank processes},
  url          = {http://dx.doi.org/10.1016/j.renene.2015.06.023},
  volume       = {85},
  year         = {2016},
}