Is hydrochar economically feasible?
Is there a business case for hydrochar? We do a quick back-of-the-envelope calculation.
Is there a business case for hydrochar?
Over the last few weeks we expressed strong reservations about a number of headline-gathering but technologically, environmentally and economically questionable prestige projects in the carbon capture space. This triggers the (fair) counter-question if we have any evidence that hydrochar production and sequestration can ever be economically feasible.
We offer a quick run-through why we are confident based on the calculations done over the last ten years that hydrothermal carbonization can reach a break-even below current market prices for carbon offset certificates.
Even if this market does not stabilize at or above current prices, hydrochar has a number of promising alternative uses for a carbon-neutral economy. A carbon offset market is an important feature to reach a carbon negative economy, but it is not a necessary feature to make hydrochar production economical. We can still go carbon neutral now and carbon negative later, once the market is up and running.
Hydrochar needs some inputs:
Biomass can be of almost any kind of origin, with biomass also having to option to be used in the production of pyrochar via pyrolysis or torrefaction. Potential substrates are:
Wood residues (sawdust, wood residues from tree felling work, roots, etc.)
Coconut tree sawdust, wood and coconut husk residues
Green waste: lawn cuttings, hedge cuttings, tree cuttings, residues from invasive plant species like water lily or lotus
Agricultural byproducts: digestate, grape / distillation / brewing residues, straw and hay, Rape plant stems, maize cob, silk cotton hull, bean-pods waste, olive mill waste, sugar cane or agave bagasse, citrus peel and pressing residues, pomace, distillation, brewing, or fermentation residues
Pretty much any kind of farm manure, poultry, pigs, and cattle being the obvious ones
Waste heat above 200°C from sewage or bio gas power plants, waste incineration plants etc.
A production plant capable to heat the wet biomass to above 180°C at approx. 10 bar pressure and supporting infrastructure — continuously, semi-continuously or as a batch process —, ideally portable to avoid transportation costs.
A major cost advantage is that hydrothermal carbonization can be implemented in small, local plants close to the biomass source. Ultimately we will see economies of scale from bigger production plants, but cross-country supply pipelines don’t seem necessary.
Hydrochar of varying carbon content (depending on substrate)
Waste heat of approx. 100°C
Waste water containing most of the nutrients of the substrate
The least valuable products formed in this process are waste heat and waste water. The former is still useful for some mundane tasks like drying processes or heating residential buildings or public swimming pools. The latter can be used do enhance performance in biogas plants or to recover the nutrients like phosphorus, potassium and nitrogen compounds.
The most valuable product in the process is hydrochar itself. It can be used to replace classical fuels in power plants and cement production, without or with less problematic salts that reduce melting temperature of the ash ( which currently prevents the wider use of fuels from biomass), for agriculture or to compensate carbon dioxide.
What is the total economic cost for producing hydrochar?
That is not that easy to answer. It depends on local conditions, transport costs, energy costs, capital depreciation, capacity utilization, and of course the cost of the biomass substrate.
There are substrates that have very clear costs (wood), are cost-neutral (grass cuttings) or are even paid for (sewage sludge). With a plant that has not yet been optimized, prices of 250€ per (metric) ton of hydrochar are already possible for green waste today. If the process is optimized, less than 170€ can be easily achieved.
If one uses raw materials that have a disposal price above 100€ per ton, this cost can be pushed well below 100€. An even lower price is rather tricky, as the process water has to be treated more intensively.
What could we possibly get in return?
If we look at the current prices for CO2 certificates, it is clear that they have risen significantly in recent years. From an initial price of around 20€, we have now reached over €70. And the curve is still rising, and the price will rise even further due to the structuring of emissions trading, as certificates are becoming more scarce.
One ton of hydrochar can compensate for about 3 tons of CO2. This means three times 70€, so you end up with a price of 210€ per ton of hydrochar. This can already be achieved today.
We can safely assume that the production costs will continue to fall in the future due to the installation of larger plants, decentralized deployment, a broader selection of substrates, the increased production of biogas in biogas plants with more excess waste heat, and most importantly, a steep learning curve from developing improved processes and end uses for the right biomass substrates.
This all shows the enormous potential of hydrochar. Very few technologies start out being close to or even above break-even.
Does hydrochar have a business case? Yes definitely!
Gerd Eberhardt et al “Rentabilität der Hydrothermalen Karbonisierung unter besonderer Berücksichtigung von Transportkosten” (Rentability of hydrothermal carbonization under special consideration transportation costs) Berichte über Landwirtschaft Hamburg (2011).
Regina Blümel et al “Endbericht Integrierte Verwertungsanlage und Strategie für kommunale Biomasse” (Final report integrated utilization plant and strategy for municipal biomass) DBFZ Deutsches Biomasseforschungszentrum for HTC Hallesche Wasser und Stadtwirtschaft (2015).