Mill implementations of biorefinery concepts are gathering momentum. It appears that the thermochemical concept (biomass solid fuel to gaseous fuel) is the preferred route at present. This is no surprise, as thermochemical gasification processes have been in use in North America for 25 years and there are at least 19 biomass gasifiers in commercial use [1]. The next step for the kraft sector will be to develop new products and markets either from the extraction and fermentation of hemicellulose, or from gasification syngas, but these involve higher risk than the thermochemical concept, where the savings from reducing energy requirement may justify the installation of the gasifier. However, it does appear that mid to long term plans for the kraft pulp industry are to find ways to benefit from the syngas route (biomass solid fuel to syngas to value-added chemical feedstocks).

Reported activities at the demonstration/mill stage include a gasification demonstration plant for the Kamloops, Domtar mill in BC. A Government of Canada grant towards the demonstration plant was a key factor. Here, the purpose is saving energy in the lime kiln. The wood-based syngas is intended to reduce natural gas consumption in the kiln and reduce CO2 emissions. The commercial-size gasifier planned for Kamloops is expected to cost around $8M and is similar to the gasifier used by Tolko, in that there are two gasification vessels [2]. The gasification process at the Tolko plywood plant in Heffley Creek, BC, started in 2006. This system recovers thermal energy from the gasification process to dry the plywood. The design for the Kamloops lime kiln requires the direct firing of the syngas in the kiln.

Other installations include a high temperature, atmospheric pressure kraft black liquor gasifier in the Weyerhaeuser mill in New Bern, NC, and a low temperature gasifier used to process carbonate spent liquor at the Norampac mill in Trenton, ON. In the case of sulphur-based black liquor, the main issue is the materials of construction. There are also three non-integrated small mills in North America that have become fossil fuel free by using biomass to create thermal energy [1]. Projects in other mills include a biomass gasification process, and ethanol production. One such example is that of Flambeau River Papers in the US, where soaring energy prices were the impetus for considering a biorefinery [3]. Here also, the involvement of the state in providing finances was a key factor. The biorefinery was considered for the mill’s steam production needs, as well as installing a state-of-the-art biorefinery pulping line. Additionally, an improved technique for extracting ethanol from sulphite pulping was planned. The recent news on Flambeau River is that they have implemented a project to recover waste energy and reduce water demand on the river. This project, which cost $190,000, will save the mill an estimated $2,100,000 in natural gas costs each year, increase production by 12 tons per day and improve operations on all its paper machines. The mill also reduced its demand on the Flambeau River by up to 1,500 gallons per minute.

1. Paper 360o, p.18, June/July 2007

2. Pulp & Paper, p.28, June 2007

3. Paper 360o, p. 18, Feb. 2007.

The biorefinery has been the subject of much discussion in the past few years. Biorefinery technologies are divided into biochemical and thermochemical processes. In the biochemical route, wood chips are pre-treated to extract acetic acid and hemicellulose. The separated hemicellulose is then fermented to ethanol and/or converted into specialty products. Identifying products that can be economically produced is a critical step in the biorefinery process. The thermochemical process is based on gasification/pyrolysis of the spent liquor. There are a small number of mills in the USA and Canada that have biorefinery projects (biomass or black liquor gasification). A sulphite mill in Canada has been converting its spent cooking liquor (by fermentation of sugars) into ethanol and specialty chemicals for some years. The mill has also recently started anaerobic biogas production.

In this competitive world, where pulp and paper can be produced much cheaper elsewhere, the biorefinery could provide a much needed edge for the North American industry. However, the biorefinery solution requires careful study of technical and economic issues to have a positive outcome.