{"id":5408,"date":"2015-03-17T21:27:46","date_gmt":"2015-03-17T20:27:46","guid":{"rendered":"http:\/\/www.theoillamp.co.uk\/?p=5408"},"modified":"2015-03-17T21:28:22","modified_gmt":"2015-03-17T20:28:22","slug":"powered-by-pee","status":"publish","type":"post","link":"https:\/\/www.theoillamp.co.uk\/?p=5408","title":{"rendered":"Powered by pee"},"content":{"rendered":"
\"bug<\/a>

Bacteria on one of my anode fibres (too few unfortunately) taken using a scanning electron microscope.<\/p><\/div>\n

A few weeks ago I heard a story about loos powered by Pee and an appeal for students to use the toilets<\/a>.\u00a0 I recognised what they were talking about since this is the area I did my doctorate in- that is microbial fuel cells.\u00a0 Microbial fuel cells (MFC’s) use the potential energy available in molecules such as glucose and derive energy from it -a process called respiration.\u00a0 All forms of respiration end up with electrons being transferred from the energy rich molecules to a terminal electron acceptor (a process of chemical reduction).\u00a0 This transfer of electrons is coupled to the formation of the universal energy currency of all living things, ATP, therefore generating energy for the organism. \u00a0 In humans our terminal election acceptor is oxygen, which is reduced to water.\u00a0 Bacteria vary in their terminal electron acceptor.\u00a0 Some can use oxygen, some anaerobic bacteria cannot but instead use a other molecules such as nitrates, organic compounds to a variety of metals.\u00a0 Some can use both oxygen and other electron acceptors depending on conditions.<\/p>\n

In microbial fuel cells we get bacteria to transfer their electrons to the anode and then we can use some of these electrons to do work (see diagram below).\u00a0 Some of the electrons must be combined with oxygen and protons produced as part of the respiration process to make water.<\/p>\n

\"mfc\"<\/a>There are two methods of electron transfer from the bacterium to an anode, indirect by naturally produced molecules or some organic dyes or by direct transfer via proteins on the surface of the bacteria.\u00a0 The latter method is preferred since its more efficient and dyes need periodic replacement.\u00a0 However not all bugs have this direct transfer ability (the ones I tried in my doctorate didn’t).\u00a0 In our bodies cells the final stages of electron transfer take place inside the cells and the same is true of most bacteria.\u00a0 Only bacteria with additional protein extensions to the outside of the cells can transfer the electrons to the anode.\u00a0 In a toilet powered by pee bacteria use urea to make electricity, the MFC could either be seeded with electrogenic bacteria or wait for a natural population to build up.<\/p>\n

The advantage of microbial fuel cells is they are at their best almost 100% efficient as energy conversion devices.\u00a0 The disadvantage is they produce very small amounts of current at low voltages (and unlike chemical fuel cells no heat).\u00a0 This low power output means they would need a huge surface area to do anything useful.\u00a0 Various niche uses have been proposed or tried, remote sensing buoys, treating brewery waste or producing electricity from sewage.\u00a0 Something such as lights in a refugee camp powered by pee is a simple but effective idea.\u00a0 The energy source is constantly replenishing.\u00a0 MFC’s are certainly not the answer to peak oil or climate change but may find some uses yet.<\/p>\n

Neil<\/p>\n

 <\/p>\n","protected":false},"excerpt":{"rendered":"

A few weeks ago I heard a story about loos powered by Pee and an appeal for students to use the toilets.\u00a0 I recognised what they were talking about since this is the area I did my doctorate in- that … Continue reading →<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_exactmetrics_skip_tracking":false,"_exactmetrics_sitenote_active":false,"_exactmetrics_sitenote_note":"","_exactmetrics_sitenote_category":0,"footnotes":""},"categories":[4,1],"tags":[102,63],"class_list":["post-5408","post","type-post","status-publish","format-standard","hentry","category-renewables","category-uncategorized","tag-microbial-fuel-cells","tag-renewables-2"],"yoast_head":"\nPowered by pee - The oil lamp - shining God's light on peak oil<\/title>\n<meta name=\"description\" content=\"A few weeks ago I heard a story about loos powered by Pee and an appeal for students to use the toilets.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.theoillamp.co.uk\/?p=5408\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"admin\" \/>\n\t<meta name=\"twitter:label2\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"2 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"WebPage\",\"@id\":\"https:\/\/www.theoillamp.co.uk\/?p=5408\",\"url\":\"https:\/\/www.theoillamp.co.uk\/?p=5408\",\"name\":\"Powered by pee - 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