Biomass residue fast pyrolysis: the future outlook
By Federico M. Berruti
February 12, 2013, Sarnia, ON - Forest and agricultural resources have traditionally been viewed as the source for only timber/pulp/paper, low grade fuels and food, whereas the emerging “green” bio-economy of Canada targets new processes to convert them into not only traditional products, but also renewable advanced fuels, chemicals, and other value-added products, such as advanced materials, pharmaceuticals and flavours.
By Federico M. Berruti
This can be accomplished by developing advanced bio-refining technologies – fractionating biomass into various valuable products, including bio-energy, bio-fuels, and bio-based chemicals and materials, as outlined in the Roadmap for Canadian Forest Biorefineries (Industry Canada, 2006).
Originally the term pyrolysis implied the slow carbonization of woody materials for the production of charcoal. Today, however, pyrolysis is being applied as the thermochemical decomposition of many types of organic matter in the absence of oxygen to produce liquid (bio-oil), solid (biochar) and gas products. The aim of these products is to create added commercial value, including chemicals, petrochemicals, and fuels, by controlling reactor operating conditions (Bridgewater, 2001).
In particular, the term “Fast Pyrolysis” is used to describe a high-temperature process (400 – 550°C) in which biomass is rapidly heated (10-200°C/s) and decomposed to form vapours, aerosols, gases and char. Bio-oil is collected by rapid quench and condensation of the vapours and by coalescence of aerosols. Fast pyrolysis processes can produce 50- 70% of liquid bio-oil, 15-25% of solid biochar and 10-20% of non-condensable product gases, depending upon the feedstock used and the operating conditions. No waste is produced: bio-oil is the primary desirable product, while biochar is also valuable and has properties that could be attractive for soil amendment (high surface area, water retention, and greenhouse gas absorption), fuel (coal or coke substitute), adsorbent for gaseous or liquid pollutants, or source of advanced carbon-based materials. The product gases can be recycled back into the process as fuel to generate the heat for reaction (Mohan, 2006).
As great as this all sounds, Pyrolysis has yet to break through into business success and, in fact, has had its fair share of failures so far. Many companies have come and gone, and there are always articles about the next greatest pyrolysis breakthrough in someone’s garage, but you never hear about it again as a commercial reality. The fact of the matter is that technical development is challenging; it took the oil industry over 100 years to be standardized and a fully successful enterprise world-wide (with many improvements and optimizations still happening today) and pyrolysis is trying to develop in a much shorter time-frame while competing with existing fuels, chemicals and government policies. In addition, bio-oil is not a quality raw crude: it has typically high water and oxygen content (more challenging for upgrading to conventional fuels), is unstable and can separate and age with time, and tends to be highly corrosive, viscous and contains some heavy tars. Suffice it to say, there are still some significant technical challenges in this “blue-ocean” new market.
In order to maximize current market opportunities and to optimize pyrolysis technology for the most promising of markets, pyrolysis companies should focus product development and testing programs around the two largest biomass contributors: wood and corn residues. The International Energy Agency (IEA) estimates the annual worldwide biomass contribution from wood to be 1.4 billion bone dry tonnes (BDt), over two times the next closest contributor, corn (WEO, 2011). Corn residues are also an important feedstock due to their fibrous nature, making them a perfect proxy for other fibrous feedstock such as sugar cane, rice and grains. Canada could particularly benefit by this strategy of development, as these feedstocks are in abundant accessible supply. In addition, Canada also has [continuously expanding] advanced infrastructure in place for low-cost biomass and fuel exports.
Heat and electric power production as well as manufacturing of renewable fertilizers and soil amendments, with potential supportive government policies and programs, could be a first step to jump start the renewable bio-oil and biochar markets, respectively. In fact, unlike direct biomass combustion, bio-oil has a very low ash content which is attractive for long-term combustion (fouling prevention). As a result of this characteristic, bio-oil is also a much better feedstock for gasification than raw biomass. Significant work has been carried out on research and development for the application of bio-oil for the heat and power generation, including the design and study of specialized bio-oil burners, engines and furnaces at CANMET (NHIRC, 2002 and Preto, 2009) and the Combustion Research Laboratory, at The University of Toronto (Tzanetakis, 2010) and also significant testing and development for power generation from bio-oil in diesel engines, gas turbines and co-firing processes (Chiaramonti, 2007 and Wissmiller, 2009). However, once the markets for both bio-oil and biochar become more established, higher-value uses will emerge for both of these products, such as specialty chemicals and materials production from bio-oil, upgrading and refining of bio-oil into conventional fuel products and upgrading of biochar for handling, energy uses and safe soil amendment purposes.
However, in order to implement technologies to harness this available energy, one must also consider that labour and transportation are the dominant operating costs, and find an optimum operating model to minimize these costs (Brown, 2011). Moreover, steady biomass availability is a challenge, being seasonal, geographically distributed and of different sizes. Stationary or centralized pyrolysis units (or wood-fired direct combustion for localized electricity production or gasification systems) require that all of the raw material biomass residue must be hauled in its raw form to the plant site, which significantly increases transportation costs and would likely limit an economic raw biomass transportation radius of under 200 km from the plant location (Badger and Fransham, 2006). However, one central plant could take advantage of economies of scale and could supply several energy users in distributed locations, while also reducing downside risk and increasing net returns (Palma, 2011). Mobile pyrolysis plants would successfully reduce raw material and product transportation costs by a factor of 2 (Badger and Fransham, 2006), but are subject to increased labour and set-up costs, depending on how often and how far the unit would need to move (Palma, 2011). An additional business model of interest has been proposed by bioliq® in Karlsruhe, Germany, where pyrolysis is performed at distributed plants and the bio-oil and biochar products are mixed together, forming a slurry, and shipped to a centralized plant for gasification to produce a high quality syngas (Bioliq, 2012). Ultimately, however, the probability of success of both mobile and stationary pyrolysis business models will heavily depend on the steady availability of feedstock and on mitigating raw feedstock costs (if feedstocks with a “negative” value are used the economics are much more favourable) and securing long-term raw material contracts, mean crude oil and natural gas prices over time, and the ability to sell/move bio-oil and biochar to the market easily (have direct bio-oil applications and an end user supply). In addition, improvements in pyrolysis technologies to further increase yields and process energy efficiency will also increase the probability of a successful business model.
Based on these considerations, one could attempt to design and finance a business that would design, manufacture and operate large-scale (>10 BDt/day) mobile pyrolysis systems, that would take advantage of both the minimized transportation costs of a mobile system, but the cost-effective nature of operating at a relatively large capacity; large enough to realize economies of scale but small enough to be realistic about how much process-worthy biomass could be in one location (to be able to operate continuously for a period of time). Notwithstanding the potential sensitivity to the aforementioned variables that would be difficult to predict in the market, one could operate over 2,200 units of this kind to process the available wood and corn residue biomass in Canada alone. This ignores any market opportunities to sell units directly to self-consuming markets in China, India and Central & South America.
Finally, a critical recommendation for the pyrolysis industry is to team-up. With government support and commitments from industry, a national consortium should be created that maximizes the “know-how” of every aspect of the production chain and connects the forestry and agricultural operators, pyrolysis experts (academic and business), market uptake, and business world. The epistemology of pyrolysis exists for all of these areas, but is fragmented – in order to push through and become a commercial success and reality, these connections are absolutely necessary. Individuals or organizations with the following areas of expertise should be part of the consortium:
• Biomass residue preparation, drying and transportation.
• Pyrolysis technology: reactor design and operation (both small and large scale; mobile and stationary).
• Biochar characterization, handling, pelletization, transportation and utilization (soil and energy).
• Bio-oil characterization, stabilization, handling, upgrading, transportation and utilization (oil & petrochemical companies).
• Business: management, financing, securing preliminary contracts and upgrading partnerships, and connecting the dots.
Federico M. Berruti, BESc, HBA, P.Eng., Ph.D. Candidate, Institute for Chemicals and Fuels from Alternative Resources (ICFAR), Western University, Vice-President, Agri-Therm Inc.
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