The Japanese wallboard producer Chiyoda Ute Co., Ltd. and its partners have developed a patented gypsum recycling process that allows the production of wallboard with up to 100% recycled content, bringing the prospect of true resource circularity to the global gypsum sector. Chiyoda Ute is part of the Knauf Group.
Chiyoda Ute (CU) is a manufacturer of wallboard and insulation materials that is headquartered in Kawagoe-cho, Mie-gun, Mie Prefecture, Japan. It is led by Yoshihisa Hirata, President of CU and member of the founding family, together with Frederick Knauf, CU’s Vice President and Representative Managing Director, as well as Country Manager for Knauf Group, in charge of integrating CU into the Knauf Group as a result of the recent public tender offer.
Thanks to its pioneering use of biomass boilers in four of its five wallboard plants, CU has been close to being climate neutral for decades. Indeed, it has halved its CO2 emissions in the past five years, mainly due to biomass use and the implementation of more efficient dryers. CU remains intent on further reducing the impact of its activities on the environment. For example, it supplies pre-cut panels according to the design of buildings for larger clients, helping reduce board waste at the site - and hence CO2 emissions. This can be as much as a 10% saving for some customers. The boards are sorted in the sequence of installation and delivered within 20 minute just-in-time (JIT) windows, further speeding up the zero waste installation process.
Sources of gypsum
The wallboard industry’s environmental impact is defined by the manufacturing process and its main raw materials, which are gypsum and board liner. Usually, this means the use of either natural or synthetic gypsum - most commonly from flue gas desulphurisation (FGD) at coal-fired power plants.Gypsum board and cement manufacturers in Japan used around 8.9Mt of gypsum in 2020. Japan lacks significant natural gypsum reserves, so there is strong emphasis on imported natural gypsum and domestic FGD gypsum. Japan imported nearly 2.3Mt of natural gypsum in 2021. With demand for natural gypsum in other developed markets likely to increase in the near future and the number of coal-fired power stations set to decrease in Japan, both of these resources will become more restricted. Securing raw gypsum will become an even more important business requirement than at present.
| Use | Gypsum Source | TOTAL | ||
| Synthetic | Natural | Recycled | ||
| Wallboard | 3959 | 1447 | 344 | 5750 |
| Cement | 2131 | 837 | 149 | 3117 |
| TOTAL | 6090 | 2284 | 493 | 8867 |
Above: Table 1 - Japanese gypsum dihydrate usage in 2020. ('000 of tonnes)
The rise of recycled gypsum
Recycled gypsum is also a potential source of 'raw' material for wallboard production, but it is taking time to reach fruition. Most Japanese wallboard producers are limited to using around 15% recycled gypsum in their board formulations, with a total of 344,000t used in 2020 in wallboard production. Some producers in Europe have achieved rates of up
to 30%.
The potential for the use of recycled gypsum in Japan, however, is higher. This is due to the short life cycles of buildings in the country, which are typically only 40 years. This means that Japan has a disproportionately large volume of waste wallboard available. Indeed, volumes of such waste are set to increase until at least 2068.
Following increases in the cost of demolishing buildings since around 2000, recent developments indicate increased tightening of regulations surrounding the disposal of wallboard. Shrinking capacities at controlled landfills are increasing the pressure to stop accepting such waste altogether, with landfill bans for gypsum already in place in some prefectures. The volume of demolition waste available represents a valuable domestic gypsum resource that could help to reduce imports of virgin materials, while drastically improving the circularity of the nation's gypsum sector. In short, the conditions are right in Japan for wallboard recycling to become well established.
Enter TCG
But how can all of this 'waste' wallboard be used? Since 2011, CU has been involved in a partnership with Tokuyama Corporation, a Tokyo-based chemical company that is the world's fourth largest manufacturer of silicon. The partners formed Tokuyama Chiyoda Gypsum (TCG), a joint venture of which CU owns a 49% stake.
TCG has developed a recycling process for used wallboard. It has operated a 40,000t/yr recycling plant at CU's 35Mm2/yr Yokkaichi wallboard plant since 2013. A second plant, this time with a capacity of 80,000t/yr, was opened at a Tokuyama site in Sodegaura City in 2016. All of the gypsum produced re-enters CU's wallboard production process.
Frederick Knauf says "When Knauf invested its resources in CU, we were surprised and delighted to discover that we had acquired the TCG gypsum process as part of the package. It was not something that had been developed beyond the laboratory scale."
TCG gypsum’s process starts with the disassembly and separation of wallboard waste at the demolition site. Foreign materials other than waste gypsum board included in the process of building demolition reduce the quality of recycled gypsum and the operation rate of the recycling plants. To ensure that only waste gypsum board is separated from the demolition site and brought to the TCG plant, the waste material collection system is an essential element of the process.
How TGC pushes the gypsum recycling envelope
However, there is a physical limit to the proportion of crushed gypsum from used wallboard that can be used in the production of new wallboard. Crushed recycled gypsum instantly absorbs water via capillary action, which leads to a dramatic increase in the viscosity of the slurry it produces. This is a major technical reason why most gypsum wallboard processes are limited to ~15% recycled gypsum in their blends.
To combat this effect, TCG has now gone beyond the simple separation, screening and scrushing of used wallboard, with the development of a patented recrystallisation process. As part of its extensive research, TCG discovered that seeding a hemihydrate solution with dihydrate crystals leads under specific conditions led to the growth of crystals to the size of natural gypsum crystals.
Compared to waste gypsum powder that was simply crushed, TCG's technology significantly reduced the viscocity of the slurry. The differences can be seen in Figures 4 - 5. The changes to the crystal structure observed led TGC to conclude that it was technically feasible to produce gypsum board made of 100% waste gypsum powder. See Figures 6 - 7.
Industrial trials
Successful trials using 100% recycled gypsum from TGC were held at CU's plant in Muroran in April 2021. To the authors' knowledge, this is the first time that any manufacturer has produced wallboard with 100% recycled gypsum content on an industrial scale. The boards passed JIS and non-combustibility tests. There were no disadvantages compared to boards produced using conventional gypsum sources, while the production process itself required only minor alterations.
CU currently holds patents for the production of wallboard comprising more than 70% recycled content. It already makes wallboard with 40% recycled gypsum content at its plants in Yokkaichi and Muroran. The company is confident that its primary resource will be recycled gypsum in the future and that this will be cost competitive with established sources.
Next steps
CU's Muroran plant is now being converted to become the first wallboard plant to use 100% recycled gypsum from TCG. The company expects to have converted this factory fully by 2026.
The physical changes at the plant will not be particularly dramatic, involving only additional reception and storage facilities. However, the establishment of reliable logistics and supply chains to ensure a reliable supply of TCG's recycled gypsum will require thoughtful consideration and development by TGC, its parent companies and various other partners. This approach has already ensured that the amount of waste gypsum board processed at TCG has increased.
On the supply side, the logistics management and the deconstruction of structures that contain wallboard have been subject to Kaizen (constant improvement). Securing the availability of sufficient amounts of recycling gypsum requires not only technical expertise, but a shared mindset too. This extends to prefecture governments and other policy makers, who will outline the regulatory landscape in which recycled gypsum can be used.
Anticipated market response
CU's four plants that use biomass can also be operated on net-zero CO2 electrical power on a campaign basis, either by using renewable power or offsetting.During July, the company is scheduled to manufacture completely climate neutral and 100% recycled drywall in its Yokkaichi factory. This will be certified by the external company WasteBox. CU will market such board and expects the market to respond very positively. Japan is a developed market that the authors feel will instantly see the benefits of such a product when it becomes available.
Concluding remarks
While the conditions currently observed in Japan make the adoption of recycled gypsum particularly advantageous, CU sees no reason why this process cannot be used elsewhere in the world. Knauf Group, as CU's major shareholder and the world's largest wallboard producer, is keenly observing developments at Muroran, which may inform its approach to gypsum sourcing elsewhere. More widely, the authors hope that CU's efforts towards 100% recycled gypsum will show that the sector can become even more sustainable in the future and act as an inspiration to others in the industry.
The work conducted by TCG's team really shows the potential of the global gypsum industry. We hope that, while the conditions are particularly agreeable for recycled gypsum to take off in Japan, this is not the only potential market. Lawmakers, not only in Japan, but around the world, should be aware that this process exists and bring forward legislation to encourage greater use of this fantastic resource. It could transform the life-cycle of gypsum into one that is truly circular, away from the traditional linear model of the past.
