Design, construction and maintenance of a Design, construction and maintenance of a biogas generator (download PDF )biogas generator (download PDF )

Design, construction and maintenance of a biogas generator (download PDF )

Design, construction and maintenance of a  Design, construction and maintenance of a  biogas generator

Biogas  generators can  be used  at  household  or  community  level  to  produce  usable fuel  and  fertilisers from human and animal waste.  This  document  covers  many  of  the  technical  aspects  of  designing,  constructing  and  maintaining  a  biogas generator however does not explore the cultural, social and education facets of the project. These should be researched separately with reference made to the case studies within this document.  
  
Introduction

Biogas  generators  extract  by-products  from  organic waste  (including  human  and  animal  excreta,  food stuffs,  etc)  which  can  be  used  to  replace  traditional fuels and fertilisers. Biogas generators produce 2 useful
products:

1.  Biogas – biogas is a natural gas which can be used directly  as  a  fuel  for  cooking  and  heating  or  used to  run  a  converted  generator  for  electricity production. 
2.  Fertiliser – digested sludge from the bottom of the biogas generator and over-flow effluent water  can be used as a fertiliser for crops  The  benefits  of  biogas  generators  are  explicitly  listed below  and  should  be  made  clear  when  suggesting  the construction  of  the  biogas  generator  to  users  in  order to improve speed and likelihood of acceptance:
1.  Biogas  generators  provide  a  safe  and  cleaner  way of  storing  excreta  and  subsequently  bring  about related advantages linked to safe sanitation
2.  Biogas  generators  provide  free  fuel  for  cooking, heating and lighting
3.  Biogas generators provide fertiliser for crops
4.  Biogas  requires  far  less  time  and  effort  to  collect than other fuels (e.g. wood)
5.  Biogas  reduces  the  need  for  wood  and  therefore reduces deforestation and the burden on women of collecting wood
6.  Biogas  creates  no  smoke  and  therefore  reduces health  problems  caused  by  burning  other  fuels indoors
7.  Biogas  is  environmentally  friendly  and  does  not release  as  many  greenhouse  gases  when  burned compared to other fuels 
8.  Dangerous  bacteria  in  faeces  are  killed  during digestion in the biogas generator 




Biogas production

Literature states that the biogas production rate of human excreta  is  0.02-0.07m3/kg/day  however  the  data  varies greatly  and  is  dependent  on  many  variables  (diet,  food intake, water intake, climate, etc). Similar  variance  is  apparent  in  human  waste  production data.  Literature  suggests  that  an  average  adult  can  be expected  to  produce  1-1.3kg  of  urine  and  0.2-0.4kg  of faeces  per  day  [7]  (if  local  figures  are  available  then  use these instead).  GTZ suggest the following production rates of biogas from wastes  of  different  animals  per  day  in  warm  climates  (in addition  to  human  excreta  other  organic  waste  such  as cattle  dung  can  be  added  to  the  generator  to  increase biogas production)

 Design, construction and maintenance of a  biogas generator

Download PDF Design, construction and maintenance of a  biogas generator (download PDF )