What future liquid fuels to heat our homes?
#FutureFuels – part 1
Liquid fuels such as oil have an important number of advantages when it comes to heating our homes, particularly in rural and remote areas not connected to the grids. They are easy to transport and ensure an autonomous and reliable supply of energy, which can be managed at the owner’s disposal.
How to keep these benefits in the future, while reducing greenhouse gas emissions?
A wide range of liquid fuels besides oil could facilitate the transition to lower-emission heating with minimal adjustments to the systems. A comprehensive study carried out by the Freiberg University of Mining and Technology in Germany identifies four main options to generate new liquid fuels: Fermentation, liquefaction, synthesis and transesterification or hydrogenation. What do these complicated names mean in practice?
(Graph: A. Awgustow, T. Kuchling, H. Wollmerstädt: Production of GHG-reduced liquid fuels, Freiberg, 2017)
{slider Fermentation}
The production of alcohol by fermentation, with the use of yeasts, is known for many thousand years. Sugar, starch or cellulose generated from wood residues is processed to produce various types of hydrocarbons, such as ethanol, ketones, alcohol or methane (biogas).
(Photo: Adobe)
{slider Liquefaction}
The thermal or chemical treatment of biomass forms liquid products, in addition to solid and gaseous substances. These liquids can then be processed to create fuels.
Pyrolysis is one of the possible processes, exposing biomass to temperatures between 200 and 1,000 °C in the absence of air, to create pyrolysis oil.
Hydrothermal liquefaction is a process similar to pyrolysis, with biomass exposed to temperatures of 300-400°C in the absence of air, but this time occurring in an aqueous environment. The liquid produced is called hydrothermal liquefaction oil or HTL oil. It is for instance suitable for the processing of algae.
(Empyro project in Hengelo (BTG-BTL), The Netherlands. Photo: Eurofuel)
{slider Synthesis}
This process consists in producing alkanes, alcohols or esters out of carbon dioxide and hydrogen, which originate from biomass or water and renewable electricity.
In the case of biomass, the “Biomass to Liquid” process involves high-temperature heating of wood, wood residues or agricultural waste, to allow for the generation of “syngas”. This syngas is then further processed through several synthesis methods to produce high-quality liquid sources of energy.
(bioliq® facilities at the Karlsruhe Institute of Technology. Photo: Eurofuel)
The “Power to Liquid” route generates syngas out of carbon dioxide from ambient, atmosphere or industrial sources, as well as hydrogen from water, through electrolysis using renewable electricity. The syngas is then processed into liquid fuels.
(Power-to-Liquid facilities at the Freiberg University of Mining and Technology. Photo: Eurofuel)
{slider Transesterification / Hydrogenation}
Using a catalyst, slightly high temperatures and a liquid environment, the structure of natural oils (such as rapeseed oil) and fats (such as used cooking oils) can be transformed into a substance more suitable for the use as fuels, fatty acid methyl esters (FAME). This is the principle of transesterification.
The other process to obtain high-performance vegetable oils is hydrogenation. The oil is processed together with hydrogen through a catalyst at temperatures around 350°C. A second stage in this method, called isomerisation, also involves hydrogen and aims to ensure better cold properties. The result of the whole process is called hydrogenated vegetable oil (HVO); it is a high-quality substance which can be admixed to diesel fuel or domestic heating oil with no limitation.
(Photo: Adobe)
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Other #FutureFuels articles
Part 2: New liquid fuels... out of biomass and waste?
Part 3: New liquid fuels... out of the sunshine?
Part 4: New liquid fuels... out of algae?
Part 5: Future fuels: Climate friendly... and affordable?
Interested to learn more?
Register to our workshop on Future Liquid Fuels, which will take place in Brussels on Wednesday 6 June 2018.