On farm anaerobic digesting

Categorie(s): Agriculture, Sustainable Energy, thematic lessons


Anaerobic Digestion is one of the more promising biological technologies for sustainable waste management. It has the potential to turn a large and worsening agro-headache into a growing opportunity for sustainable farming. It can extract useful biogas energy and high quality fertilizer from manure and other agro waste products while reducing the air and water pollution and emissions of greenhouse gases from a farming operation. Anaerobic Digestion harnesses natural living biological processes to maintain the natural carbon cycle and extract useful energy and fertilizers from the waste streams. Many types of farming could use it.

Read On Farm Anaerobic Digesters and answer the questions below.
Farmers are happy to use the system, as you can read in the news item ‘Pig manure, sweet money’

The article is quite long, work in a small group and let each read one part extra carefully. Answer the questions together. The student knowing the answer on a question explains the others why this is the right answer.
Read the whole article AFTER working on the questions.

Decide together which questions you still have on the subject.
Perhaps your teacher can help, or somebody else. Or, better still,  go to a farm and discuss with the farmer why he has this system on his farm, or why not.

Maybe you can help building a first simplified system: when you put cow manure in a big plastic bag and wait some days, you can harvest some biogas already, so simple systems are not too difficult to build…


  1. The text calls the system ‘Anaerobic Digesters’. What is meant with ‘anaerobic’ and what with ‘digesting?’
  2. Many people make from their organic waste already compost. What is the difference between composting and the ‘digestion’ in this text?
  3. What is the difference between the digestion of food in your stomach and guts and the digestion in this text?
  4. How do farms in your region dispose of their waste? If you do not know, you could organise a field trip to a farm and find out.
  5. Make a list of the dangers of just disposing of the farm waste into rivers, lakes etc.
  6. Bringing the manure on the fieldes is in fact an old and good practice – in farms of 200 years ago. In modern farming this practice is very harmful. What has changed in farming practices to make this no longer ‘good’?
  7. Anaerobic systems to produce biogas out of waste is already happening in many places. What makes it better when done on the farm?
  8. Why must it be anaerobic? Which useful product would anyway not be formed if it were aerobic?
  9. Which nutrients can be kept inside a farm with this system?
  10. Why does this system prevent the foul smell of farming?
  11. Why must a farmer using this system avoid pesticides?
  12. Methane is a powerful greenhouse gas. But when it is burnt you get carbondioxyde, also a greenhouse gas. Why is it better to bring CO2 in the air than methane?
  13. Make a list of all the positive aspects of ON FARM ANAERBIC DIGESTORS as compareed with tradional ways of getting rid of your crap.