{"id":2019,"date":"2020-08-05T13:35:23","date_gmt":"2020-08-05T13:35:23","guid":{"rendered":"http:\/\/wp.lancs.ac.uk\/recirculate\/?p=2019"},"modified":"2020-08-24T15:20:23","modified_gmt":"2020-08-24T15:20:23","slug":"blog-the-acid-test","status":"publish","type":"post","link":"http:\/\/wp.lancs.ac.uk\/recirculate\/2020\/08\/blog-the-acid-test\/","title":{"rendered":"The Acid Test"},"content":{"rendered":"

Research to develop\u00a0<\/span><\/span>anaerobic digestion\u00a0<\/span><\/span>systems<\/span><\/span>\u00a0<\/span><\/span>to<\/span><\/span>\u00a0<\/span><\/span>produce sustainable energy\u00a0<\/span><\/span>and\u00a0<\/span><\/span>a safe fertilizer for use in sustainable food production<\/span><\/span>.<\/span><\/span>\u00a0<\/span><\/span>\u00a0<\/span><\/strong><\/p>\n

Anaerobic digestion\u00a0<\/span>(AD)\u00a0<\/span>is a naturally occurring microbial process\u00a0<\/span>combined with\u00a0<\/span>carefully designed\u00a0<\/span>e<\/span>ngineer<\/span>ing\u00a0<\/span>to convert human, agricultural and other organic wastes\u00a0<\/span>efficiently\u00a0<\/span>into biogas for use as a fuel. For instance, commercial AD system<\/span>s<\/span>\u00a0<\/span>use on<\/span>–<\/span>site industrial organic waste to generate heat and power<\/span><\/a>. O<\/span>ther d<\/span>edicated waste treatment units\u00a0<\/span>use locally generated\u00a0<\/span>organic wastes, from\u00a0<\/span>markets or agriculture<\/span><\/a>, and\u00a0<\/span>human waste (from toilet systems)<\/span><\/a>\u00a0<\/span>to generate electricity.\u00a0 At the other extreme,\u00a0<\/span>AD can use domestic waste to produce biogas as a cooking fuel<\/span><\/a>.<\/span>\u00a0<\/span><\/p>\n

T<\/span>he use of AD to produce biogas is a remarkable example of applied microbiology.\u00a0<\/span>In a typical AD system, organic components in the raw materials are converted to organic acids by a set of microbes known as \u201cacidogens\u201d. Then a different set of microbes (\u201cmethanogens\u201d) convert the organic acids to a mixture of carbon dioxide and methane.\u00a0<\/span>The<\/span>\u00a0methane is the key component of biogas.\u00a0 However, there is a problem because too much acid is damaging to the methanogens. This limits the production of methane and the conversion of waste to energy.\u00a0 As a result, in many AD systems much of the organic material remains undigested.\u00a0<\/span>\u00a0<\/span><\/p>\n

At the end of biogas production AD leaves a by-product (digestate) that is rich in nitrogen, phosphorus and other essential plant nutrients.\u00a0 As a result, digestate\u00a0<\/span>has the potential to be a low-cost, locally produced fertilizer for use in sustainable agriculture<\/span><\/a>. However, the use of digestate is limited because, without additional treatments,\u00a0<\/a><\/span>it can remain contaminated by disease-causing microorganisms (pathogens) present in the original waste material.\u00a0\u00a0<\/span>Contamination can be a problem with food waste, for example obtained from municipal solid waste (\u201cgarbage\u201d).\u00a0 It is also a problem with animal manures and especially w<\/span>hen\u00a0<\/span>the raw material for AD includes\u00a0<\/span>human waste, for example from pit toilets or sewage systems<\/span>.\u00a0<\/span>\u00a0<\/span><\/p>\n

The additional treatments needed to eliminate pathogens from digestate can include using some of the biogas produced to heat the digestate. This \u2018pasteurizes\u2019 the digestate but can also divert a substantial fraction of the biogas produced.\u00a0 Other\u00a0<\/span>heat or chemical<\/span>\u00a0treatments add significant extra costs.<\/span>\u00a0<\/span><\/p>\n

The combined problems of limited gas production and pathogen contamination of digestates have\u00a0<\/span>constrained<\/span>\u00a0the adoption and proper implementation of AD systems, especially in developing countries.<\/span>\u00a0<\/span>Improved uptake of AD need<\/span>s<\/span>\u00a0<\/span>system<\/span>s<\/span> that maximize biogas yields AND minimize pathogen load.\u00a0 While there are many different designs for AD systems, <\/span>no one<\/span>\u00a0<\/span>has<\/span>\u00a0produced a system that is\u00a0<\/span>optimized to deliver both these goals. This dual optimization is the focus of my research within the\u00a0<\/span>GCRF<\/span><\/a>-funded RECIRCULATE project.\u00a0\u00a0<\/span>We are using engineering solutions to separate\u00a0<\/span>the acid<\/span>-producing<\/span>\u00a0and methan<\/span>e-producing stages of AD.\u00a0\u00a0<\/span>\u00a0<\/span><\/p>\n

This is what we call a \u201ctwo-stage AD process\u201d.\u00a0 The first stage is known as a plug flow acidogenic reactor or \u201cPFAR\u201d.\u00a0 That simply means that the waste materials enter as a series of batches at one end of the system.\u00a0 Successive batches then flow progressively through the system until they exit at the other end. You can almost think of it like a conveyor belt.\u00a0\u00a0<\/span>We design the PFAR stage to maximise the production of o<\/span>rganic acids<\/span>\u00a0by acidogenic microbes<\/span>.\u00a0 The partially digested, acid-rich material from Stage 1 becomes the feedstock for Stage 2. The second stage is referred to as a continuously stirred tank methanogenic reactor (CSTMR).<\/span>\u00a0We design the CSTMR stage to optimise the activity of\u00a0<\/span>methanogen<\/span>s.\u00a0 This achieves the most efficient conversion of organic acids\u00a0<\/span>from Stage 1\u00a0<\/span>to\u00a0<\/span>methane,\u00a0<\/span>and so m<\/span>aximise<\/span>s\u00a0<\/span>overall\u00a0<\/span>energy<\/span>\u00a0production.\u00a0\u00a0<\/span>\u00a0<\/span><\/p>\n

At this\u00a0<\/span>point,<\/span>\u00a0you may be asking,\u00a0<\/span>how does the\u00a0<\/span>two-stage<\/span>\u00a0process help with reducing pathogen contamination<\/span>?\u00a0 In theory<\/span>,<\/span>\u00a0<\/span>high\u00a0<\/span>acid<\/span>ity is damaging to pathogenic microbes as well as methanogens.\u00a0<\/span>By carefully managing the flow of material through the stage 1\u00a0<\/span>process,<\/span>\u00a0we can ensure that organic acids build-up to such high concentrations that they kill the pathogen<\/span>s<\/span>.\u00a0\u00a0<\/span>Efficient acid production during Stage 1 could be the key step to allowing digestate to be used as a safe fertilizer as well as optimising energy production<\/span>.\u00a0\u00a0<\/span>\u00a0<\/span><\/p>\n

That\u2019s the theory but how does this work out in practice?\u00a0 My research to date has focused on Phase 1.\u00a0 Using lab-scale AD systems I have confirmed that the\u00a0<\/span>PFAR approach is very effective at killing a range of pathogen<\/span><\/a>s. Even better, the system is more effective at breaking-down the raw materials compared to existing single stage AD. For example, two of the main components of the raw\u00a0<\/span>material are cellulose and lignin.\u00a0 In\u00a0<\/span>our<\/span>\u00a0<\/span>systems,<\/span>\u00a0we<\/span>\u00a0find that about 40% of the cellulose and 56% of the lignin is broken down within\u00a0<\/span>four weeks<\/span>. That compares with\u00a0<\/span>about 18%<\/span>\u00a0cellulose and\u00a0<\/span>16<\/span>% lignin in typical single stage AD.\u00a0\u00a0<\/span>The next steps will be to ensure that this greater\u00a0<\/span>breakdown<\/span>\u00a0during Stage 1 is translated in to enhanced biogas yields at the end of the Stage 2 CSTMR process.<\/span>\u00a0<\/span><\/p>\n

The safe and efficient AD processes we are developing will not only produce biogas as a fuel but digestate as fertilizer\u00a0<\/span>to boost crop production<\/a><\/span>. To achieve that my\u00a0<\/span>engineering\u00a0<\/span>research interfaces with RECIRCULATE\u00a0<\/span>research across multiple academic disciplines.\u00a0\u00a0<\/span>RECIRCULATE\u2019s<\/span>\u00a0interdisciplinary research\u00a0<\/span>in the\u00a0<\/span>UK<\/span>,\u00a0<\/span>Nigeria<\/span><\/a>,\u00a0<\/span>Ghana<\/span><\/a>\u00a0and beyond\u00a0<\/span>aims to deliver solutions for multiple sustainable goals<\/span>\u00a0(SDGs<\/span>)<\/span>.\u00a0<\/span>\u00a0<\/span>Our sister\u00a0project\u00a0<\/span>ACTUATE<\/span><\/a>\u00a0will build demonstrator AD systems so that we can get the views of local communities on the best designs for their needs.\u00a0<\/span>The\u00a0<\/span>\u2018headlines\u2019 may be to contribute to\u00a0<\/span>Good Health and Wellbeing (<\/span>SDG<\/span>3)<\/span><\/a>\u00a0by improved handling of human and other wastes, which also directly helps\u00a0<\/span>SDG6 (<\/span>Clean Water<\/span>\u00a0and Sanitation)<\/span><\/a>.\u00a0\u00a0<\/span>However,\u00a0<\/span>the\u00a0<\/span>RECIRCULATE\u00a0<\/span>project\u00a0<\/span>does not see those SDGs in isolation<\/span>.\u00a0\u00a0<\/span>Our new<\/span>\u00a0<\/span>two-stage AD design\u00a0<\/span>is a key part of that.\u00a0\u00a0<\/span>Once we have\u00a0<\/span>optimize<\/span>d<\/span>\u00a0our design then it will\u00a0<\/span>allow us to go beyond\u00a0<\/span>SDGs 3 and 6\u00a0<\/span>to\u00a0<\/span>contribute to\u00a0<\/span>SDG7 (<\/span>Affordable and Clean Energy<\/span>)<\/span><\/a>\u00a0and\u00a0<\/span>SDG2 (Zero Hunger<\/span>)<\/span><\/a>\u00a0<\/span>as well<\/span>.\u00a0<\/span>\u00a0<\/span><\/p>\n\n\n\n
\"Bhushan<\/td>\nBhushan Gandhi <\/strong>is a graduate researcher working at Lancaster University, UK and is completing a PhD funded by Lancaster University contributing to Work Package 4 (Water for Energy Production) of the RECIRCULATE project. Bhushan has Masters degrees in Environmental Science & Engineering from the Indian Institute of Technology Bombay, Mumbai, and in Biotechnology from M.S. University of Baroda, Vadodara and a BSc in Biotechnology from Pune University, India. Before coming to Lancaster he worked for a pharmaceuticals company in Ahmedabad, India.<\/em><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

 <\/p>\n

All articles in The FLOW<\/strong> are published under a Creative Commons \u2014 Attribution\/No derivatives license,<\/a> for details please read the RECIRCULATE re-publishing guidelines<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"

Research to develop\u00a0anaerobic digestion\u00a0systems\u00a0to\u00a0produce sustainable energy\u00a0and\u00a0a safe fertilizer for use in sustainable food production.\u00a0\u00a0 Anaerobic digestion\u00a0(AD)\u00a0is a naturally occurring microbial process\u00a0combined with\u00a0carefully designed\u00a0engineering\u00a0to convert human, agricultural and other organic wastes\u00a0efficiently\u00a0into biogas for use as a fuel. For instance, commercial AD systems\u00a0use on–site industrial organic waste to generate heat and power. Other dedicated waste treatment units\u00a0use […]<\/p>\n","protected":false},"author":910,"featured_media":2048,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2},"jetpack_post_was_ever_published":false},"categories":[44,38],"tags":[],"class_list":["post-2019","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-the-flow","category-wp4"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"http:\/\/wp.lancs.ac.uk\/recirculate\/files\/2020\/08\/Reactors-1-cropped.jpg","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p9hFf1-wz","_links":{"self":[{"href":"http:\/\/wp.lancs.ac.uk\/recirculate\/wp-json\/wp\/v2\/posts\/2019","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/wp.lancs.ac.uk\/recirculate\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/wp.lancs.ac.uk\/recirculate\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/wp.lancs.ac.uk\/recirculate\/wp-json\/wp\/v2\/users\/910"}],"replies":[{"embeddable":true,"href":"http:\/\/wp.lancs.ac.uk\/recirculate\/wp-json\/wp\/v2\/comments?post=2019"}],"version-history":[{"count":16,"href":"http:\/\/wp.lancs.ac.uk\/recirculate\/wp-json\/wp\/v2\/posts\/2019\/revisions"}],"predecessor-version":[{"id":2856,"href":"http:\/\/wp.lancs.ac.uk\/recirculate\/wp-json\/wp\/v2\/posts\/2019\/revisions\/2856"}],"wp:featuredmedia":[{"embeddable":true,"href":"http:\/\/wp.lancs.ac.uk\/recirculate\/wp-json\/wp\/v2\/media\/2048"}],"wp:attachment":[{"href":"http:\/\/wp.lancs.ac.uk\/recirculate\/wp-json\/wp\/v2\/media?parent=2019"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/wp.lancs.ac.uk\/recirculate\/wp-json\/wp\/v2\/categories?post=2019"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/wp.lancs.ac.uk\/recirculate\/wp-json\/wp\/v2\/tags?post=2019"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}