There is a potential for producing a significant amount of marketable compost from organic waste. In LCA perspective, the produced compost can be used for agricultural purposes to replace conventional fertilizer. As reported in literature, one tonne of good-quality compost can be used to replace chemical fertilizer, since there is a possibility to supply the essential nutrients at the rate of 7.1 kg of nitrogen (N), 4.1 kg of phosphorus (P2O5) and 5.4 kg of potassium (K2O) per tonne of compost (Patyk, 1996). However, these values are quite old. Does anyone know the amount of conventional fertilizer (kg of N, P2O5, and K2O) which can be replaced by applying one tonne of good quality compost (based on recent research)?
1. The amount of nutrients contained in compost is a function of the original material (type of manure, industrial waste, etc) and the composting process. From my corner of the world, here is a link to a document on agriculture composting. Note table 3 for source material contents and table 4 for types of composting. Second link is a document from Cornell U that shows range of analysis for dairy/poultry manure compost. We also have the largest composter in North America here that uses municipal wastes from various streams (third URL)
http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex8875/$file/400_27-1.pdf?OpenElement
http://cwmi.css.cornell.edu/compostfs4.pdf
sorry - hit the wrong key - ..... to continue.
Below is a link to a fact-sheet of our municipal composting facility. Compost is sold through a wide range of outlets and retailers in and around the city. I do not have an analysis for their product(s).
2. Consider application method and loss of nutrients. Some nutrients such as potassium won't go anywhere while Nitrogen will be lost to the atmosphere depending upon how the compost is made, how it is applied and incorporated and, ambient conditions. Thus, I would discount the nitrogen content of compost by up to 50%.
3. From an LCA point of view be aware of the range of energy expenditures of the composting process as well as the energy expended to produce the source material (attribution issues!). If you are considering greenhouse gases, composting can result in N2O and CH4 emissions.
Dear Goddard,
Many thanks for your reply. You have pointed out few important points that I should consider in my analysis. Thanks for sharing the links related to composting.
As you correctly pointed out, loss of nutrient throughout the process should be accounted. Finally the aim is to credit the avoidance of chemical fertilizer as a reward of compost production.
I have accounted GHG emissions from all the phases of life cycle of compost production.
Thanks again for your reply.
Dear Menikpura,
One cubic meter compost can contain 2 kg N, 0.6 kg P and 2 kg Ca, but this depends on compost materials.
Dear Nirmala:
Also, It could be necessary to consider that not all the total content on the compost will be available 100% in a period of time. As Dr. Llinkin said, depend on the type of compost (source and process) and also of this othe important aspect. Other aspect: the final percentage of nutrients available depends on the nutrient. Nitrogen for instance, could be 50% of the total en few months but other nutrient as P or K, this percentage could be different.
This is a difficult question to answer because in the question are incorrect assumptions, delivered by the petrochemical industry. First of all, is P2o5 the form of Phosphorus that we want? Next, it ignores the concepts that Carbon and Sulfur are essentials. So it prevents talking about water retention, humates, fulvic acid.
This brings me to another point: Sure I can beat the American "green revolution methodology" that was deployed globally and has destroyed soil, worldwide. BUT, an organic solution, to be better than a conventional fertilization program, needs to know your region, your rainfall, your soil sample. How an organic approach can solve problems requires data.
For example, I have fed off P deposits for 2 years on farmland, so no P add-on was needed. I used P that conventional chemical driven farmers do not know how to access.
besides to the total amount of elements their availability should be taken in account?
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