We were recently tasked by one of our prospective customers, a large paint manufacturer, of estimating carbon savings by using solvent recycling in comparison to their existing process; buying new solvents and disposing of them (often, although not in this case, to incinerator).

Calculating carbon footprint of new solvents was made easy thanks to some excellent European research.  It is easy to see that new solvent manufacture creates huge quantities of CO2, between 1,600-6,000kg for every 1,000kg of solvent produced.

Not knowing the origin of the solvents, if they are imported or not, we simply added a conservative figure for transport from a local supplier to the customer and likewise for collecting the used solvent.  In the same vain, we can’t know if the disposed solvents are then recycled or incinerated (to our knowledge usually incinerated, since recycling mixed solvents is somewhat complex), but in any case we didn’t add CO2 for burning.

Then, calculating the energy usage of our machines to recycle the solvent is also quite complex.  Whilst easy to come up with some rough figures, we were keen to be able to calculate more accurately depending on the solvent at hand.  The difficulty here is that each solvent has a different boiling point, each requires differing amounts of energy to heat by 1ºC (called “specific heat”) and different amounts of energy to then change from liquid to gas (i.e. evaporate, called “latent heat of vaporisation”).  These two values change with temperature, and obtaining value curves for every solvent would be extremely difficult.  Therefore, we’d have to settle with using just one value for each.  We’d also have to calculate how much diathermic oil there is to heat, how much steel and how much heat loss. Add to this the fact you can run single batches in our machines, continuous batches or even continuous loading, different factory shift patterns, workdays, ambient temperature and so on, meant there are lots of options to consider.

Once the energy is calculated, we convert this to carbon/CO2 generated using the U.K.’s National Grid figures for 2020.

Some machines use a plastic bag so we’ve accounted for those, too.

Whilst we can’t say these figures are scientifically entirely accurate, we can be confident that they are a very good indication of savings.  In this case, and no doubt others, the savings are massive, both monetarily and, the key focus here, towards the environment.

Carbon footprint was reduced by over 97%.  That means that this one factory could help generate 358,631kg less carbon per year.

Whilst it’s doing that, it will save in the region of £64,000 per year….not bad considering someone is paying this customer for their waste currently!