In what aspect do they differ from one another?

Gábor Z. Szelényi yes would love to explain this and there are quite a few observations which I can list them here and few of them which came to my knowledge are : The environmental impact of an organic manure unit (such as a biogas plant or anaerobic digester) can vary depending on several factors, including: These are listed below:

1. Type of feedstock (e.g., food waste, agricultural waste, sewage sludge)

2. Scale of operation

3. Technology and design

4. Management and operation practices

Here are some potential environmental impacts of organic manure units:

Positive impacts:

1. Renewable energy production (biogas)

2. Reduced greenhouse gas emissions (by capturing methane)

3. Nutrient-rich fertilizer production (digestate)

4. Waste reduction and management

Negative impacts:

1. Odor and noise emissions

2. Pathogen and microplastic contamination (if not properly managed)

3. Water pollution (if effluents are not properly treated)

4. Land use and habitat disruption (if large areas are used for feedstock production)

Differences between mesophilic and thermophilic digestion:

1. Temperature: Mesophilic (30-38°C) vs. Thermophilic (50-55°C)

2. Microbial communities: Different species dominate at different temperatures

3. Pathogen destruction: Thermophilic digestion is more effective at killing pathogens

4. Biogas production: Thermophilic digestion can produce more biogas, but may require more energy input

Differences between small-scale and large-scale units:

1. Energy balance: Small-scale units may not generate enough energy to power themselves

2. Cost-effectiveness: Large-scale units can benefit from economies of scale

3. Management complexity: Large-scale units require more sophisticated management systems

4. Environmental impact: Large-scale units can have a larger environmental footprint

It's important to consider these factors when designing and operating organic manure units to minimize negative impacts and maximize benefits.

Srinivas Kasulla If I understand correctly, by you meant the treatment of biogas digestate. What did you mean by ?

Gábor Z. Szelényi Yes i do agree and in India the terms used by most of the Biogas Plant owners is the same so I had to use the terms so that it would be easy for the Indians to understand whereas no doubt worldwide it is called as the digestate - both the terms organic fertilizer and organic manure stands for the same

Srinivas Kasulla Thank you for the explanation. In this case your list of factors is valid and nearly complete, only the assessment document is usually organized in a different order:

It consists of a Technological summary + Impacts of the activity on the #1 Air quality; #2 Soil; #3 Surface water; #4 Underground water; #5 Waste treatment; #6 Noise/Vibration; (#7 Nuclear radiation - luckily, non applicable for digestates)

Supplementary remarks:

- There will be some inevitable emission of residual methane gas from the digestate, even after applied on the agricultural land. This goes to the air quality chapter.

- The same applies to ammonia, largely present in digestates. Even if treated the most carefully possible, only 50 - 60% of the NH3 is taken up by the agricultural crops and the soil microbes. The rest evaporates to the atmosphere. The only consolation is that, at least, NH3 is not a greenhouse-gas. Mitigation measures are part of the air quality chapter.

- We do not expect toxic metals in agricultural feedstocks, but there may be some in municipal wastewater. This concerns the soil quality chapter.

- Persistent organic chemicals may occur in both feedstocks. If yes, they are to be discussed in the water quality chapters.

- Microplastic pollution is a recently recognized problem, and unfortunately there is no reliable technology to mitigate it at present. The only measure a biogas plant can take, is prevention: careful treatment of the feedstock. This can be treated in the technological summary, not in the environmental chapters.

- If the product of the biogas plant is biomethane, there is a substantial fire/explosion risk. Again, the prevention is part of the technological summary.

Gábor Z. Szelényi Thankyou for the assessment order and yes this would be surely helpful for my future research on Digestate production units in India