Brewing biomass

E&T reports on the International Biomass Combustion case studies.

The use of biomass instead of fossil fuels is gaining acceptance as a cost effective form of renewable energy as the price of fossil fuels increases.

Whether as a boiler fuel to generate process steam or co-generate steam and electricity, biomass is starting to be favoured over fossil fuels.

Biomass can be obtained from a variety of sources such as wood chips, cardboard, sawmill bark, sawdust, rice husks, sugarcane bagasse and refuse derived fuel pellets.

The International Biomass Combustion case studies include multiple Brazilian brewery biomass combustion boiler installations, a Belgian brewery biomass combustion feasibility study and a Jamaican sugarcane bagasse combustion feasibility study. These studies include an evaluation of process steam generation for use on-site at the Brazilian breweries, co-generation for combined heat and power to produce process steam for use on-site, and electricity for use on-site and also for distribution to the local power grid for the Belgian and Jamaican studies.

Brazilian Brewery Biomass-Fired Boilers

The switch from heavy fuel oil to biomass for combusting in process steam boilers at multiple Brazilian breweries resulted in significant operating cost savings.

In 2003, 16 AmBev breweries in Brazil used heavy fuel oil to generate process steam, with a combined annual heavy fuel oil usage of 68,930 tonnes. This represented 47 per cent of steam boiler fuel usage among the 26 breweries in Brazil, with the remaining 53 per cent provided by natural gas at the other ten breweries.

The AmBev Biomass Project started in 2004 with four projects developed with steam suppliers, where AmBev paid for steam consumption in the Lages, Agudos, Cuiabá and Teresina breweries and the steam suppliers located biomass process steam boilers on the brewery sites.

In 2006, AmBev developed a biomass project in-house where all biomass combustion and steam generation was conducted by AmBev at the Viamão brewery. The biomass-fuelled steam generation plant was designed for: minimum biomass storage area for five days of operations; automated biomass feed input; two boilers each rated at 19 tonnes of steam per hour; automated bottom and fly ash removal system.

The biomass boilers combined are able to generate 38 tonnes of steam per hour to meet brewery production process steam requirements. The consumption of biomass for steam generation is 3,000 tonnes of rice husks or 4,000 tonnes of wood chips per month - rice husk and wood chips were selected due to the abundant local supply and low cost. Rice husks cost 25 per cent of heavy fuel oil per unit of boiler steam output, and wood chips 40 per cent. The heavy fuel oil-fired boilers previously used at the site remained to serve for emergency steam supply in case of any problem with the biomass boilers and to prevent any interruption to the supply of steam.

Between 2004 and 2006, the Biomass Project in AmBev developed over five sites and included additional fuels such as babaçu coconut husk.

The total annual operating cost savings in 2006 was R$8,050,000 (US$3,659,000) for the five breweries listed. Project activities at the Viamão brewery have decreased greenhouse gas (GHG) emissions by the use of biomass in place of heavy fuel oil in boilers at 28,000 tonnes of carbon dioxide equivalent (Co2e) per year. This does not include the Co2e reductions from the other breweries.

By 2007, seven of the 26 AmBev breweries were using biomass to generate process steam, thereby displacing a combined annual heavy fuel oil usage of 56,129 tonnes. This represents 34 per cent of steam boiler fuel usage among the 26 breweries. There were eight breweries still using heavy fuel oil with an annual usage of 20,191 tonnes, which represented 12 per cent of steam boiler fuel usage. The other 11 breweries were using natural gas for boiler fuel, which represented 54 per cent of steam boiler fuel usage.

Bottom and fly ash resulting from biomass combustion is being mixed with sludge from the brewery's wastewater effluent treatment in a composting process, thus resulting in the production of a soil fertiliser. The possibility of selling the bottom and fly ash to the ceramics industry is also being considered, which may yield a higher selling price for the ash.

The AmBev Biomass Project in Brazil was developed in accordance with United Nations framework Convention on Climate Change (UNFCCC) methodology. As of May 2007, the project is under UNFCCC validation for the Clean Development Mechanism, simplified Project Design Document for small-scale Project Activities (SSC-CDM-PDD) Version 02.

Belgian Brewery Co-generation Feasibility study

For many countries in Europe, the costs of fossil fuels and electricity have risen to the point that renewable energy projects are financially feasible.

However, the role of government financial incentives is equally important to the success of projects. European companies have a strategic need to reduce GHG emissions, with a proposal from the EU for 20 per cent renewable energy by 2020 and EU 'phase 2' carbon dioxide reduction targets for 2008. Carbon trading markets and government incentives make a positive business case for many RE projects.

The Belgian brewery biomass co-generation feasibility study was conducted with a design objective of producing 15 tonnes of steam per hour and 1.5MW of electricity prompted by financial incentives from the Belgian government. The high-pressure steam was used in a steam turbine to produce electricity with residual steam used for brewery processes.

The Co2 reduction for this study was estimated to be 20,000 tonnes per year, and would be equivalent to €400,000 in carbon credits in addition to the annual €2,000,000 natural gas fuel cost savings.

There would also be a reduction of 3,500 truck trips per year to avoid transporting the spent grains to end-users as animal feed. This reduced truck traffic is equivalent to 500 tonnes of GHG per year in addition to reducing road congestion in the vicinity of the brewery.

Combusting spent brewer's grains as a boiler fuel is not currently commercially viable, but with declining spent grain prices in many districts in Europe and rising fossil fuel prices there is interest in conducting research in this area. The current limitation is economically dewatering and drying the spent grains, which requires considerable energy input. Research concepts include blending the mechanically dewatered spent grains with a dry biomass stream such as wood chips to create a blended biomass fuel mixture that can sustain combustion without having to thermally dry the spent grains.

Jamaican sugarcane Bagasse Co-generation Feasibility study

Conceptual designs were developed for sugarcane bagasse combustion and co-generation plants for combined heat and power using available biomass by-products from sugar mill operations in Jamaica.

The technical and financial feasibility of biomass co-generation for on-site electricity and steam use and surplus electricity export to the Jamaican domestic market were evaluated. Three sugar plantations were studied including a significant evaluation of drying and storing the biomass for combustion throughout the year, as the sugar harvesting and processing operations only last for six months per year.

The following parameters were evaluated: available biomass quantity and seasonal variability; sugar mill energy usage for fuel oil and electricity; fuel properties of sugarcane bagasse including high heat value, ultimate analysis, moisture content and bulk density; air emissions for combustion of biomass as compared to the existing fuel oil fired boilers; potential electrical and steam production from a high efficiency boiler and steam turbine; cost estimate to purchase and install the fuel handling, boiler, steam turbine and electrical equipment; and life-cycle financial analysis with annual costs and revenues to determine the internal rate of return.

The Jamaican sugar industry is experiencing external and internal economic and political influences that make it difficult to attract foreign capital investment.

Despite the potential for much needed decentralised power co-generation at Jamaican sugar mills to provide stable electricity for rural districts, there will not be any development of biomass co-generation facilities until the government is able to work effectively with foreign investors and upgrade the sugar industry infrastructure to compete with other sugar exporting nations such as Brazil and India.

Steven Law PEng, is a project engineer for Earth Tech Canada. Extra info details of the AmBev project:

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