From biomass and waste
The Summer School Renewable Gas (RenewGas), proposed by BioEco Graduate School, focuses on two renewable energy carriers (H2 and CH4) obtained from renewable feedstocks (biomass and waste).
Most energy scenarios, stablished to guide de energy politics, are based on three pillars: energy sobriety (avoid wasting energy), energy usage efficiency (improving systems to reduce their energy consumption) and non-renewable energy sources replacement by renewable ones. This summer school will be focused on two renewable energy carriers (H2 and CH4) obtained from renewable feedstocks (biomass and waste). H2 and CH4 may assume two main roles in energy transition: energy carrier and energy storage medium.
The summer school will cover H2 and CH4 production from feedstocks to gas distribution and storage, including a strong focus on biological and thermochemical production process.
Biomass and waste are organic matter based on carbon, hydrogen, oxygen, nitrogen and sulphur. Two main challenges arise to convert these feedstocks: they are heterogenous and broadly spread in the nature. The summer school will treat about these feedstocks, their availability and composition, and whether the composition and properties of a specific feedstock may guide the technology choice for its conversion.
The conversion processes
We may split the conversion process in two main stages: conversion process itself (the reactor) and the cleaning and upgrading of the gas to reach to specifications required downstream (a second stage of reaction, storage, or injection into the transportation network). Reaction step processes may be divided in two groups (biochemical process and thermochemical process) depending in the phenomena that drives the reaction. The summer school will be structured following these groups.
– Biochemical processes :
Biochemical processes are mostly wet methods at low temperatures and pressures where biochemical reactions are driven by a large group of bacteria. Three main processes will be treated :
- Anaerobic digestion treats solid or liquid feedstocks. The course will cover that happens with organic matter during digestion, going into biological reaction. Required properties of feedstock to reach an efficient methane production will be discussed together with different existing process configurations. Each process step-up has its pros and cons, they will be discussed and connected to inhibitions processes, main limitations of the technology and the influence of these key points on the digestor stability. Several case-studies will help to explain all these crosslinked phenomena and how a digestor may be driven.
- Methanation treats a gas to convert it into methane. This gas might be a blend of H2, CO, CO2 (syngas coming from a gasification process) or a blend of CO2 coming from a capture process and hydrogen coming from an electrolysis process (power to gas). Main reactions schemes will be cover in relation with constraints and limitations of a gas based reaction system in aqueous phase. Biological reactor architecture responding to these challenges will be presented.
- Bio-hydrogen production by biological methods will be the opportunity to present the overall hydrogen sector. The course will then focus on the biological technology process, including reactors set-up, mechanisms, catalyst, and pros and cons of each choice. Finally, the biological production step integration in a whole chain will be covered.
– Thermochemical processes
Thermochemical processes gather a large panel of high temperature processes with different atmospheres (inert, air, steam, CO2 and blends). Most of these processes are gas-solid reaction processes. The summer school will focus on the three main thermochemical processes to produce hydrogen and methane.
- Gasification is a thermochemical process that includes several steps to crack organic matter into a blend of H2, CO, CO2, CH4, COVs, tars… called producer gas or synthesis gas (syngas). The course will follow the different steps of this conversion, basics reaction mechanisms and interactions between solid matter and gas. Different reactor set-up will be discussed, identifying advantages and main limitation of each technology.
- Catalytic Methanation is high temperature and high pressure catalytic process allowing the recombination of H2 and CO2 or CO to build CH4. The course will be focused on catalyst, their chemical and physical form in order to improve yield and selectivity. Typical methanation catalytic processes will be also covered.
- Hydrothermal processes are arising as a potential technology to produce CH4. They have also been studied for H2 production. They are wet methods using water at high pressure and temperature as reaction media. Basics of hydrothermal process for H2 and CH4 production will be addressed.
– Gas cleaning and separation processes
Both biological and thermochemical processes do not produce pure products. They produce a blend of molecules; few of these molecules must be removed to reach downstream operation inlet specification.
- Gas cleaning. A general overview of the gas cleaning technologies will be done, including different separation operations, like adsorption, absorption, particle filtration…
- Membrane gas separation. A specific focus will be done on gas separation using membranes. Mechanism fundamentals and membrane properties will be discussed. Its application to CH4/CO2 separation and H2 separation will be described.
- PSA (Pressure Swing Adsorption) technology. PSA is also an important technology for hydrogen and methane purification. The course will treat on PSA semi-batch operation processes basis. The adsorption support choice depending on the objective will be also treated.
Gas network and storage
Actual natural gas network is optimized to distribute fossil natural gas to final users. However, a replacement of fossil natural gas by bio-methane requires a rearrangement of the network design and management. The French natural gas network will be described, as well as the processes and methods required for the biomethane injection into the network. These renewable gas energy carriers allow mid and long term storage; this is a major asset of this kind of renewable energy carriers.
Storage will be described and a specific focus will be done on underground massive gas storage, including deep saline aquifers. The course will cover the development of the aquifer and the storage site design. A real case of hydrogen massive storage in deep saline aquifers will be used as example.
French, European and International master students (M2) and PhD students