That is correct. The effluent (‘Liquor' or as I like to call it ‘digestate’) from the AD or the anaerobic digester is recycled back to crop/pasture/hay lands associated with the dairy farm. Therefore the nutrient cycle is closed. In Canada there are environmental regulations we should follow when applying the digestate to crop and pasture lands. As long as ‘best management practices’ are followed, in terms of digestate management (this same regulations apply to raw manure as well), there are no major issues.

In addition to economic returns from electricity, AD has other ecosystem services. For example, fertilizer value of digestate is roughly 10-20% higher than the fertilizer value of raw manure, since organic matter in raw manure is mineralized in the process. This will lead to farmers needing less chemical fertilizer. Also, digestate has significantly less pathogens, weed seeds, and odor.

There is some concern regarding increased NH3 and N2O emissions after digestate application to lands compared with raw manure application. However, research results show that this is far outweighed by the decrease in CH4 emissions achieved by adopting and AD in dairy farms. There are several LCAs (Life Cycle Analysis) in the published research to prove that.

Susantha

Justification for a technology of future use will definitely consider sustainability. Therefore economic justification can be done by calculating the cost of the present practice by the diary farmers and comparing it with an estimated cost of the future tech. Compare the labour costs and deprivations of the present and future technology. Also economic justification for a biogas digester may require that you estimate the potential market demand in relation to production/assemblage cost.

Dear Paria,

 Did you have any data from these project or any references about this issues in your country, I will appreciate .if you send any of it.

regards

Dear Fikrat,

This project has not been installed and practically exploited in massive sizes in Iran due to unreliable economical conditions and lack of justification. Hence, I believe that the first step after feasibility and potentiality studies is satisfying dairy farmers from economical points of view.

best regards

A possible approach is to run a BMP test to figure out the amount of recoverable methane. Then you can use this value to estimate the revenue from electricity sale (or generally energy sale). You can use NPV method to estimate the cost of investment to establish the project.

Less lesive environmental impact

Regional and local developemt

Technology rate

Economic results

Social impact

Contribute to reduce climate change

Hello Paria,

The web link given here provides a freely available spreadsheet workbook that was designed for determining economic feasibility of a farm-based AD: www.bioeconproject.com

Note that this workbook may not be directly applicable to your dairy farm situation as it has been developed for dairy farms in Ontario (a province of Canada). However, it may provide some useful information for you to identify what type of background data needed for performing such an analysis.

Economic feasibility of a bio-digester for dairy farms depends on the general characteristics of the dairy farming sector and type of agricultural/environmental policies in a particular country.  In Ontario, government promote AD technology in medium to large size dairy farms for renewable energy generation and greenhouse gas mitigation by providing financial incentives such as ‘guaranteed pricing’ for renewable electricity generated and financial assistance in construction.

Further useful information on this spreadsheet workbook can be found in the following paper:

Anderson et al. (2013) An economic and functional tool for assessing the financial feasibility of farm-based anaerobic digesters. Renewable Energy 51: 85-92.

Hope this information would help you.

Paria, 

 Justifications are directly related to the size of the supply (daily, weekly) of substrate.  This dictates the size, in KW, of the digester and its corresponding electrical output.  Of equal importance is the heat generated in addition to the electrical output.  These two products happen to be identical in quantity. The heat "by-product" can be captured for secondary electrical generation. So you must start with the amount of substrate (cow manure in this case) available.  All of this is just the beginning as the biogas and heat generation are just the first phase.  Once the "liquor" is produced it needs to be directed into aerobic lagoons for 17 days to destroy the pathogen and further digest the substrate, now liquor.  Following the 17 days of aerobic treatment, the wastewater is ready for the final phase of treatment and polishing.  Completion of the aerobic phase is determined by the BOD levels.  Once your BOD target is met, the second lagoon finishes the wastewater treatment in an anaerobic environment with an algae cap.  Again the BOD levels determine the finished product.  The algae is harvested as the finished polished wastewater is pump into circular irrigation systems on agricultural crops  (I pump about 21 million gallons of treated wastewater per year) where the nutrients are recycled and the water is transpired by the crop to precipitate out in the form of dew within 200 KM. Your pathogens are put through anaerobic, aerobic, anaerobic environments with the final spray being hit by UV and oxygen again as it is irrigated.  Soil moisture monitors provide daily feedback to facilitate optimum transpiration.  

The photo above is a SEM photo of some of the psychrophilic algae I use in winter. Since I am in Canada I use combinations of mesophiles ( 6 months the year) and psychrophiles (6months of the year).  The cooling conditions even in Iran will dictate the use of cold loving algae. The algae is used for animal feed. 

Send me an e-mail if you want to talk further as I have Power Point Presentations on all this. 

Best Regards

Jon 

We are having a project on biogas production in ASRII,it is in the beginning stage,but finaly economical evaluation is done,but it depends upon to the situation and area of the biogas plan,we can think about compost fertilizer also from this project also.

Paria, 

Reza is correct.  The ability of the substrate to generate methane (the glacial age producing gas) is the first component of the economic justification.  However, to operate biogas facilities without the other phases of nutrient recovery and energy production is a make a poorer case for the economic justification.  If you have sufficient substrate of good quality then you can produce the biogas economically.  So lets start with a few fact based questions:

How many cows are on the average Iranian dairy farm?  

What variety of dairy cow is it (more size related than anything else)? 

Once you give me those figures I can tell you what you can produce for electricity. 

I await your reply. 

Dear Cloud,

Thanks for your contribution in this discussion. Actually, I need to know whether there are some economical techniques to conduct a feasibilty study on biogas production or not. At present, I have not chosen a specific dairy farm but in Iran, we can find various herd sizes (small (5000)). of course, I want to help dairy managers to decide better to install a biogas digester or not. I am looking forward to recieving your valuable comments.

Thanks

Dear Susantha Jayasundara,

I found your information very helpful and constructive. I ask for your further assistance on this subject.

Great thanks!

Dear Paria,

I am glad that the information I provided were useful.

Our medium to large size dairy farms fall in the size range of 50 to 3000 animals/farm.  Holstein is the most dominant breed (about 95% of herds).  Average milk production is about 30-35 kg/day.  Feed is high quality (72-75% TDN). Methane potential is satisfactory.  We also encourage co-digestion with off-farm material, originating from the food processing sector.  Government assistance plays a huge role in establishing this technology in our dairy farms.  You may find some lessens from our farm-based bio-digesters that may be applicable to your farms.  Here is another more simpler document you can use for a  quick financial assessment.

Susantha

Start by reviewing the availability of electrical power and other fuels to the farm.  Then look at the regulations that impact the availability.  In one US state, the farms could produce enough gas to be able to sell electric power back to the local electric company.  However, the local electric company had gotten the state legislature to set the price at which the power company had to accept this power was below the cost of production for the farmer.  So the farmer was left with the only option of using the gas generated and converted into electricity to reduce their purchase of electricity from the power company.  This was a case of the power company just not wanting to have to deal with the issue of small power generators.

Edward,

What a bummer.  It is not the case in Canada. The political will in very different even though we are major oil and gas suppliers to the US and world.

i think, along with the cost and output calculations, simple logic is also required while proposing any new system. For example, who will manage this bio-digestor, what will happen to the waste output ? And dont forget the cost of periodical maintenance. These small things can be  solved through simple logic, bt should not be avoided

When we look at an issue like this we do a "What's in it for ME" chart.  In this analysis, any individual or entity that has an interest whether positive or negative is shown.  Then each relationship is explored to understand why each would take that position. Once you understand who has a vested interest in the success or failure, then you can begin to formulate an approach to each to deliver results.

Bhanu,

Since the substrate is dairy cow manure, the proceed product, referred to as "liquor" is applied in liquid form to the crop fields (usually alfalfa and corn) post harvest.  The nutrient load remaining depends to the largest degree to the quality of inputs the cows received.  The liquor has significant value when the NPK of the liquor is analyzed. 

That is correct. The effluent (‘Liquor' or as I like to call it ‘digestate’) from the AD or the anaerobic digester is recycled back to crop/pasture/hay lands associated with the dairy farm. Therefore the nutrient cycle is closed. In Canada there are environmental regulations we should follow when applying the digestate to crop and pasture lands. As long as ‘best management practices’ are followed, in terms of digestate management (this same regulations apply to raw manure as well), there are no major issues.

In addition to economic returns from electricity, AD has other ecosystem services. For example, fertilizer value of digestate is roughly 10-20% higher than the fertilizer value of raw manure, since organic matter in raw manure is mineralized in the process. This will lead to farmers needing less chemical fertilizer. Also, digestate has significantly less pathogens, weed seeds, and odor.

There is some concern regarding increased NH3 and N2O emissions after digestate application to lands compared with raw manure application. However, research results show that this is far outweighed by the decrease in CH4 emissions achieved by adopting and AD in dairy farms. There are several LCAs (Life Cycle Analysis) in the published research to prove that.

Susantha

Sorry. do me a favour please, I shall make a final project concerning feasibility study of biogas plant from cow manure but in my country there is no, in fact I had already  a research proposal seminar with the title "economic feasibility study of biogas plant from cow manure" but after being tested by the lecturer for undergraduate it is too high to me, and now I would like to narrow the scope only of it's electricity side only, so do me a favour, I had tried searching the literature but I didn't get anywhere.

Dear Riki,

Try RETScreen (www.retscreen.net), it´s a free tool for Life Cycle Cost Analysis. It will allow you to estimate the yearly production of biogas from manure of your herd of cows (beef or dairy cattle), depending of their weight. After that crucial information, the tool will help you to estimate the competitiveness of your biodgester to generate biogas-power & heat. You´ll need to input cost of biodigester, engine and heat recovery system. Also, you´ll need some financial information, but many case studies are available to guide you.

I hope it helps. Regards,

Luis

The concept of recycling the manure back to the land has worked for hundreds of years when it was done on a relatively small scale.  Today, when the farm operations operate (in the United States) with hundreds to thousands of cows the recycling of manure becomes a question of economics.  The economic investment in recycling equipment is difficult to recover with the relatively low cost of electricity due to the low petroleum prices (in the United States).  The operating cost is driven up by the regulatory environment.    The question that seems to be missing in many analysis are what are the cost offsets that occur with AD.  The unfortunate reality is the bankers only look at the traditional return on investment when funding these projects.  The critical issue is to define what will be impacting the cash flow based on the investment; both positively and negatively.

https://books.google.com.tr/books?hl=tr&lr=&id=px_h3gsNsf4C&oi=fnd&pg=PR1&dq=economical+justification+of+a+future+renewable+energy+project&ots=mKVYD81cdx&sig=2p5OfLRQSnIEitC2FoCKujwWFRo&redir_esc=y#v=onepage&q=economical%20justification%20of%20a%20future%20renewable%20energy%20project&f=false

Article Energy Storage for Mitigating the Variability of Renewable E...

http://aapt.scitation.org/doi/abs/10.1119/1.12352?journalCode=ajp

Thanks Hamit

How about Cost Benefit Analysis?

Thanks Denista. I agree! CBA is a good solution.