Benefits for farmers and dairy companies

For farmers and dairy companies, the motivation to produce biogas is simple.  It will reduce their costs while providing an additional source of revenue.

 First, let’s look at the opportunity to reduce costs for dairy farmers.  The use of home grown power allows farmers to become self- sufficient by using the electricity made from their cow manure to power their farm.  The amount of electricity that a dairy farm uses every week is significant, primarily because of the refrigeration of the milk and the electric milking machines.

 An example of how much electricity a dairy farm would normally use is the Haubenschilds' dairy farm that uses 9,000 kw every week.  With the electricity rates in Ontario ranging from 6,3 to 11,8 cents/ kWh they would be spending on average $900 dollars a week and $45 000 dollars a year! Not having to pay for electricity would make a huge dent in their annual costs.

Another cost reduction is heating by cogeneration.  When the generator is using the biogas to produce electricity, 60% of the energy used is lost in the form of heat.  Cogeneration projects trap the heat created by the operation of the engine and use it for various tasks such as heating water and heating rooms.  

 

The other benefit for farmers is revenue:  This biofuel provides four major sources of income:

-          Sale of electricity

-          Carbon offsets

-          Sale of livestock bedding

-          Sale of liquid fertilizer

 

The first source of income for the farmers is the production of electricity.  Because most farms use the biogas to produce electricity, the surplus can be sold to utility companies as green energy. The Ontario government has put in place a green energy price of 11 cents/ kwh (14 cents at peak hours) so that the farmers get more in return.  The farmers can also sell the biogas to gas utility companies because it is similar to commercial natural gas.

Carbon credits are another source of income for the farmers.  Companies who need to offset the greenhouse gases they’re releasing into the atmosphere want to buy carbon credits from others.  Farmers who produce biogas from manure are able to claim amounts of carbon credits by avoided methane emissions.

The last source of income is the sale of bedding and fertilizer.  In my recent post I explained that during the digestion anaerobic bacteria separates the manure in to its primary components so the methane rises and is trapped at the top of the digester.  But what happens to the rest?  Post digestion offers two different types of waste: liquid and solid.  The first type, liquid waste, can be used as fertilizer for crops.  Due to the transformation of nitrogen to ammonium in the digester, farmers are able to reduce the quantity of fertilizer applied, allowing dairy farms to sell more of it.  The solid waste that comes out of the digester can be used as bedding for animals.  By using the digester, farmers are able to eliminate most of the bacteria, making animals less prone to pathogens within the bedding. The unused bedding can then be sold to other farms.

 

The bedding here is coming out of the digester and is then being used in the farm. 

 

Another interesting thing that dairy companies and farmers can do is invest in community digesters.  Because most dairy famers in Canada don’t have enough cows on their farm to benefit from having a digester, the installation of one would have no economic gain.  A solution to this is installing a community digester that is centrally located so that the surrounding farms can use it. This is a benefit to dairy companies because it means that their farms can still have a place to put their manure and still allow them to be self sufficient with electricity, bedding and fertilizer.    

The savings for farmers, combined with the additional source of revenue would be an incentive for the installation of a digester.  The total cost for a farm to install one depends on how much of the work and design they do for themselves- the purchase of the actual digester only accounts for 35-40% of the total cost. Other costs are the purchase of the land, the amount and prices of material and labour input for excavation and installation.  The total price of the digester is normally around 300,000$!  However in time the digester will pay for itself.

 

Comparing a farm with a digester and one without:

 

Diagram of a farm without an anaerobic digester.

Diagram for a farm with a digester.

These are two diagrams that show the differences of a farm with an anaerobic digester and one without.  The red arrows represent all of the negative products that come from dairy farms.  The first diagram has methane emissions, odour and run off as negative products.  These are each serious consequences by themselves and when added together result in extremely high amounts of pollution.  The second diagram has no negative products because the anaerobic digester has been installed and instead has positive products that result from the digestion.