In the RESTORE project, SINTEF has calculated the climate effects of different treatments of residual flows from a farm. Different residual materials have been looked at and whether they can be composted, incinerated or used in biochar production. A spreadsheet model has been created that provides some answers on the economics, quantity produced and climate footprint of different alternatives.
Here we have looked at the calculation for the production of biochar at Mære. In the example, we assume that we have 2000 lm3 (loose cubic meters) of dry wood chips (20% moisture), which corresponds to 500 tons of product.
Fixed and variable costs can be included in the model, here is an example of costs for biochar plants. These are expensive plants and whether it is a sensible investment will depend on the revenue sides: sale of biochar and heat and possible subsidies for use and carbon storage. Subsidies for the investment are also possible.
The spreadsheet calculates the amount of biochar and the amount of hot water we can get from the production, compared to a base scenario, which in this case is wood chip firing. When firing in a wood chip boiler, we get almost twice as much hot water (but no biochar). Here, the energy price is set at 1 NOK/kWh and the biochar price is set at 10,000 NOK/ton.
In the production of biochar, about half of the available carbon is stored in the charcoal compared to full combustion. This charcoal can then be stored for at least a hundred years and is therefore out of the cycle. When we use biochar on the field, we expect a smaller proportion to break down in the first few years, but at least 80% will be stable for over a hundred years (or many hundreds).
Here, secondary emissions are set to zero. There will be some use of fossil energy for transporting and chopping wood chips. For the production of wood chips, Environmental Agency a figure of 7 grams CO2e/kWh which would give 9.3 tons of CO2e for this amount of wood chips.
We have also calculated emissions and costs of composting. (and you can see this here)
The spreadsheet prepared by Sintef is available by contacting us.
