System Processes for citric acid

Question

Hi,

I've been working with citric acid databases recently and found myself a bit puzzled by the different processes listed in ecoinvent v3.10.

Only system processes are available, and they vary by input material. For example, there are processes like:

• citric acid production / maize starch

• citric acid production / citric acid

• citric acid production / energy feed

Each process lists the respective type as the main product on the output side, which makes sense for citric acid, but not for maize starch or energy feed, since these are clearly input materials.

My understanding is that the other flows in these processes are normalized to, say, 1 kg of maize starch input — since maize starch isn’t actually an output of the process.

I'm looking forward to hearing your thoughts on this — and perhaps getting a bit of clarification. :)

Cheers!

Answer 1

Indeed, these are somewhat funny processes, they are system processes even in the unit process versions of ecoinvent and result of an applied allocation, where also maize starch and energy are products of of the process before the allocation. After the allocation, indeed everything in each process is scaled to the respective product and its amount listed, so e.g. to 1 kg maize starch.