Many of my posts are looking at how the energy efficiency of wastewater treatment can be improved. In fact one of my first posts was looking at exactly this. At large municipal wastewater treatment works that are constantly treating the waste produced by whole towns any little piece of energy they can save will help them cut costs. If we really could reduce energy usage down to zero for wastewater treatment, what sort of effect would that have on a country like Germany?
So the energy usage of wastewater treatment is part of “Other” in the above chart. How much of “Other” is it?
You see that little red strip up there? That is total energy usage of all wastewater treatment plants in Germany when compared to other industries. Although only a small blip on the chart I have shown it adds up to one of the larger energy consumers for municipalities. This is all good, but what if we start looking at industry and some of the bigger pieces of the pie?
One interesting idea is to treat the highly concentrated wastewater from certain industries on-site. This makes the job of the municipal wastewater treatment works easier and should help reduce fees for wastewater disposal required by the factory. Some places where this makes sense include: paper production, milk processing, meat processing and abattoirs, and many food and beverage production facilities. The processes produce waste streams with very high organic loading, that can often be treated using anaerobic digestion.
A big advantage of anaerobic digestion that often gets touted is its ability to produce biogas as a potential energy source. This should make it super attractive to industries that need a system for treating their waste, right?
Well… Maybe. The big factor that comes into play is cost. Let’s say we are living in a perfect world where the treatment plant is running and most of the cost has been offset by the fewer waste disposal fees the factory now has to pay. What about all that biogas being produced? How much of an effect would the energy recovered from biogas production have on a large factory? Let’s have a look at energy costs for industrial use in Germany for an example week, the blue line below is the continuous average price of energy in €/MWh.
What the hell is happening at the end there?!?! The actual price of energy is negative, people are paying me to use more energy now or what? Yes, actually. Even if you ignore the negative prices (the phenomenen for which the priority given to renewable energy is often blamed) it is possible to see the change in energy prices even within a single day. If you are running a large factory and someone says you can save so and so much money by building a biogas plant and processing your waste into renewable energy and someone else comes and says you can save even more money by just running one of your production lines a bit later in the evening, which option do you choose?
So at the moment energy does matter but money matters more.