Establishment of Carbon Cultivation-Based Fuel Production Technology
In a carbon-circulating society, biomass produced by carbon cultivation is used as an alternative energy source to fossil resources. Biomass can be a stable renewable energy source, but it is difficult to procure in large quantities. Therefore, it is strategically important from an energy strategy perspective to establish technologies to produce fuels with high efficiency from a wide variety of biomass, which is especially demanded by energy companies and large-scale consumers, and to construct a local production for local consumption energy system for local consumers that takes advantage of the characteristics of biomass use.
Hydrogen is expected to be the ultimate clean energy because it produces only water during combustion; it can be produced, stored, and transported from diverse energy sources, including renewable energy; and it can be used in all areas of power, transportation, heat, and industrial processes to decarbonize the world. However, current major hydrogen production technologies use fossil energy as a raw material, and the CO₂ emissions derived from this are a major challenge. In Japan, the Basic Hydrogen Strategy was formulated in 2017 at the Ministerial Conference on Renewable Energy and Hydrogen, which calls for the steady development of a wide range of innovative technologies for hydrogen production, transportation, storage, and utilization to realize a hydrogen society in the medium to long term up to 2050, with a view to the full-scale diffusion of hydrogen use. In addition, in 2021, the U.S. Department of Energy will launch the "Energy Earthshots Initiative" and set an ambitious CO₂-free hydrogen cost target (80% reduction within 10 years) in the first phase, the "Hydrogen Shot", and other national hydrogen strategies are now in motion in many countries around the world. Biomass is expected to be a stable raw material for hydrogen, and the development of hydrogen production technologies through thermochemical conversion of biomass, such as gasification, pyrolysis, and steam reforming, as well as fermentation hydrogen production technologies using microorganisms, is underway.
Against this background, this study will focus on the development of a CO₂-free hydrogen production process using biomass as a feedstock as a medium- to long-term issue, and the development of a liquid fuel production process using the same basic technology as this as a short- to medium-term issue.
An important issue for the social implementation of biomass fuel production technology is the reduction of production costs. In addition, the components of biomass feedstock are diverse, and their composition varies greatly depending on the type of feedstock, making it difficult to meet a wide range of demands with uniform technology. To solve these issues, it is necessary to select, integrate, and innovate technologies based on comparative studies of various thermochemical and biological conversion technologies. This R&D will promote the development of technologies in such different fields in an integrated manner, enabling the construction and expansion of a flexible biomass fuel supply system tailored to regional/feedstock needs.
We are developing a small-scale decentralized biomass steam gasification system that aims to produce hydrogen through biomass gasification at atmospheric pressure and low temperatures (550-650°C). Our goal is to discover low-cost and high-performance biomass gasification catalysts as well as tar reforming catalysts. These catalysts will be utilized in a compact, standalone biomass steam gasification system.
The conversion process of cellulose and hemicellulose present in lignocellulosic biomass, such as rice straw, has gained significant attention. However, the current dominant conversion method, enzymatic hydrolysis, faces economic challenges due to the high cost of enzymes. Therefore, we are developing a two-stage hydrothermal saccharification process for rice straw using a reusable solid acid catalyst, eliminating the need for enzymes.
Bioconversion: Biohydrogen production/Liquid biofuel production
Biological hydrogen production utilizing microorganisms offers the advantage of operating at ambient conditions, resulting in minimal environmental impact. Furthermore, it enables the development of a zero-emission process through CO₂ recycling, using biomass as the feedstock. Our research group, in collaboration with Sharp Corporation, has achieved an impressive hydrogen production rate (up to 300 L H₂/h/L) utilizing a dark fermentation hydrogen production pathway involving formic acid. Building upon this high-speed hydrogen production process, we are working on improving hydrogen yield by introducing heterologous hydrogen-producing enzymes (hydrogenases) through genetic engineering. This advancement allows for the construction of novel hydrogen-producing microorganisms capable of producing up to four moles of hydrogen from one mole of glucose. Additionally, we are engaged in technology development aimed at establishing an integrated process with photofermentation, theoretically enabling the production of up to 12 moles of hydrogen from biomass feedstock (sugar).
We have been advancing the development of metabolic engineering technologies using coryneform bacteria, industrially valuable microorganisms with a long history of application in amino acid production. In conjunction with this, we have also developed our proprietary growth-independent bioprocess known as RITE Bioprocess®. The combination of these technologies enables the highly efficient utilization of non-edible biomass-derived sugars, establishing a high-yield bioprocess that demonstrates significant advantages in terms of fermentation inhibitor tolerance and simultaneous utilization of mixed sugars. Building upon these foundational technologies, we are constructing an integrated liquid fuel production process from a wide range of non-edible biomass feedstocks and obtaining proof-of-concept data to move towards practical applications.
In recent years, there has been growing interest in the technology of producing hydrogen through steam reforming as an upgrading method for bio-oil. Steam reforming of natural gas has already been industrialized, and while its reforming technology is readily transferable, catalytic deactivation has been a challenge when dealing with oxygenated compounds like organic acids as feedstock. We have been investigating catalyst sintering and coke formation mechanisms, leading to the development of Ni and Nd@CeO₂-Al₂O₃ catalysts using core-shell catalysts and CeO₂ with oxygen storage capacity. These catalysts offer higher hydrogen yields and longer lifespans, even when applied to steam reforming of organic acids, addressing the issues associated with catalyst deactivation.
Bio-oil Reformation by Novel Catalysts
The production of bio-oil through rapid pyrolysis of biomass has garnered significant attention due to its effectiveness in directly converting a substantial portion of biomass constituents into liquid fuels. However, bio-oil obtained from the pyrolysis process is composed of a wide range of oxygenated compounds, typically exhibiting high viscosity, strong corrosiveness, and chemical instability, presenting challenges in terms of storage and handling. In this study, we are developing HZSM-5-based zeolite catalysts to upgrade bio-oil generated from high-speed pyrolysis of biomass on-site. Additionally, we are investigating the mechanisms that influence catalyst performance and catalyst preparation.
Production of Liquid Fuel from Bio-oil by Hydrogenation
We are developing novel high-performance dual-function (hydrogenation-deoxygenation/isomerization/cracking) catalysts and technology to produce bio-jet fuels in a one-step process using feedstocks such as palm oil and palm fatty acid distillate (PFAD).