calculating MSW to SAF LCA

To model a Msw to FT pathway directly there are a couple of steps to take.

1. Set the FT fuel properties on the Fuel Char sheet to match those of the SAF that you are producing. The energy and volumetric densities and the carbon content of the fuel are the important ones.

2. Set the RDF fuel properties on Fuel Char to be the same as the RDF and make sure that it is representative of your feedstock. The energy density is critical.

3. If the fuel processing information is included in the mass and energy information is included in the fuel production information then you can zero out the RDF stage. In column CA on the input sheet zero the electricity and all but 0.001 MJ of NG

4. Adjust the mass input in column CA so that the upstream emission for the SW to RDF pathway is zero except for the avoided emission.

5. With these changes the RDF to FTD pathway will become a MSW to SAF pathway.

6. The avoided emissions have three parameters that can be set. The first is the methane emissions from MSW from a landfill. This is cell F48, the default value is 90 g CH4/dry kg of MSW. The second is the renewable C content of the MSW, cell F44 (default is 0.70) and finally the fraction of methane avoidance that will be accepted in a regulatory system (F45).

The avoided methane emissions in column CA gets carried through to the FTD pathway and shows up as avoided emissions there.

I hope that this helps.

Don O'Connor

The hydrogen consumption is entered on the Alt Fuel Production sheet. The pathway is in column E and hydrogen is n row 44.

The units are kg/litre.

Regards
Don O'Connor

Your should use the energy density for the RDF value on the Fuel Char sheet.

To turn the RDF to FT pathway to a MSW to FT pathway, set CA 243 to zero and CAS 245 to 0.1.

Then adjust CA 247 until DY11 on the upstream emissions sheet is 0. A value of 95.4 will do it for the default, but the value will be different after you adjust the energy content of your RDF.

Don O'Connor

Most FT plant designs in the public domain are very large and they generate their own electricity and thermal energy requirements from the waste heat generated by the process, so the need for external electricity and NG is avoided.

The FT process is not very energy efficient so there is a lot of excess heat, especially when a resource like MSW is being gasified (again not very efficient).

Regards
Don O'Connor

As a default value it can be used for both cases.

The value could be adjusted if you have some better process design data for the two different scenarios.

Regards
Don O'Connor

Wen
You have to have a small input into the electricity or NG cells to avoid a div zero error but a very small number can be used there so that it has no impact on the results.

Regards
Don O'Connor