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 is difficult to procure in large quantities. Therefore, from an energy strategy perspective it is important to establish highly efficient technologies for producing fuels from a wide variety of biomass, and there is particular demand for such technologies from energy companies and large-scale consumers. It is also vital to construct systems for local production targeted at local consumption of energy by local consumers, and such systems should take advantage of the characteristics of biomass use.
Hydrogen is expected to be the ultimate clean energy, since 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 for decarbonization in all kinds of sectors, including power, transportation, and heat and industrial processes. Currently, however, major hydrogen production technologies use fossil fuels as a raw material, and the resulting CO₂ emissions are a critical challenge. In Japan, the Basic Hydrogen Strategy formulated in 2017 at the Ministerial Conference on Renewable Energy and Hydrogen 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 US Department of Energy launched the Energy Earthshots Initiative and set an ambitious CO₂-free hydrogen cost target (80% reduction within 10 years) in the first phase, dubbed the "Hydrogen Shot." 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 production, and the development of hydrogen production technologies is under way. These include thermochemical conversion of biomass, such as gasification, pyrolysis, and steam reforming, as well as fermentative hydrogen production technologies using microorganisms.
Against this background, this study will focus on the development of CO₂-free hydrogen production processes with biomass as a raw material as a medium- to long-term theme, and the development of liquid fuel production processes making use of the same basic technologies from biomass as a short- to medium-term goal.
One of the key challenges for the social implementation of biomass fuel production technology is to reduce 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 and feedstock needs.
We are developing a small-scale separated-type biomass steam gasification system that aims to produce hydrogen through biomass gasification at atmospheric pressure and low temperatures (550-650°C) with the minimum tar generation. Meanwhile, we are discovering low-cost and high-performance biomass gasification catalysts as well as tar reforming catalysts, which will be utilized in the above biomass steam gasification system.
The conversion process for 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.
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 fermentative 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. Additionally, we are engaged in technology development aimed at establishing an integrated process with photo fermentation, theoretically maximizing hydrogen yield from biomass-derived sugars.
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 a 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 advanced liquid biofuel 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 technology for producing hydrogen through steam reforming as an upgrading method for bio-oil which could be obtained from gasification and pyrolysis of biomass. Steam reforming of natural gas has already been industrialized, and while reforming technology is readily transferable, catalytic deactivation has been a challenge when dealing with oxygenated compounds like organic acids as feedstock. In order to avoid sintering of active metal, and to inhibit coke formation, we have been developed a series of Ni/Al2O3 core-shell catalysts in which the shell of Al2O3 protected the Ni particles from sintering, and Ni/CeO2-Al2O3 catalysts in which CeO₂ with oxygen storage capacity was added onto the shell, and inhibited the formation of coke. These catalysts occupied higher hydrogen yields and longer lifetime, even when applied to steam reforming of organic acids, addressing the issues corresponding to the catalyst deactivation.
The production of bio-oil through rapid pyrolysis of biomass has garnered significant attention due to its efficiency in directly converting a substantial portion of biomass constituents into liquid fuels. However, the bio-oil obtained from the pyrolysis process is always 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 high-performance catalysts such as HZSM-5-based zeolite catalysts to upgrade the bio-oils generated from rapid pyrolysis of biomass on-site. Additionally, we are investigating the mechanisms that influence catalyst performance and catalyst preparation in order to obtain more excellent catalysts for bio-oil upgrading.
We are developing novel high-performance multi-function (hydrogenation-deoxygenation/isomerization/cracking) catalysts and technology to produce bio-jet fuels or sustainable aviation fuel (SAF) in a one-step process using feedstocks such as palm oil and palm fatty acid distillate (PFAD). Also, the technology has been developed to apply into the production of bio fuel oil or SAF from various bio-oil obtained in the different ways, especially from the gasification and pyrolysis of biomass.
