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Tuesday, March 5, 2019

8th Nordic Wood Biorefinery Conference: detailed review

I realise that I promised this review back in October. Time goes on and life interferes; but better late than never. So here goes.


The 8th edition of this conference attracted about 200 people, largely from Sweden and Finland, but also from Asia, Europe, South America and Canada. This report builds on daily conference outlines by the author, and published by VTT (click here). The conference concluded with the announcement of the next NWBC, to be held in Stockholm at the Hotel Courtyard, 24-26 March, 2020.

Business and policy context

A series of keynote speeches and panel discussions set the tone. Berry Wiersum of SAPPI described the current context as a period of intense change and innovation. Technically this is a good time to be involved in research and development. But huge policy battles are brewing in Brussels, with forest owners, forest companies, oil companies, the EU Parliament and NGOs involved, all tugging in their individual directions. The key driver is this: Brand-owners such as Nestle, Unilever or Coca-Cola want low-cost, light weight, thin, recyclable barrier coatings against water, air and grease; this is where R&D needs to focus. Separately, there is a strong political need for the forest sector to become more energy efficient, even if it is true that the industry’s energy needs are largely met by burning carbon neutral fuels. From a business perspective, these carbon neutral fuels consist mainly of lignin, and far more value can be unlocked if the lignin is used elsewhere. Are deep eutectic solvents a solution? This technology is still a long way in the future. A very interesting view from industry.

In a second keynote speech, James Clark, University of York, described our society as chemically-dependent, and asked whether carbon neutrality means a new metal dependency. Rare metals are needed in many low-carbon technologies; what is the carbon impact of these? There are lots of sustainability issues just in the batteries for electric cars – cobalt, lithium – let alone in solar panels or other renewable energy technologies. Many of these metals are now, or soon will be, in short supply, and metal recovery from landfilled wastes will become critical. Separately, most pathways for converting to a bio-based chemistry will lead through platform chemicals. Ethylene, propylene and BTX are likely to be replaced by platform chemicals from biomass, such as published lists of Top 20 (UK) or Top 12 (US). The aromatic functionalities will be most challenging. Downstream chemistry also needs to change to use these new platforms. Reduction and hydrogenation will take precedence over oxidation. A parallel pathway to chemical fractionation is thermochemical decomposition, with ‘controlled’ depolymerization the key. Selectivity, control, deconstruction, depolymerization, fractionation are key technologies. Several of these pathways are still far from commercial, however.
In a panel discussion, Bernard de Galembert of CEPI, James Clark, Mike Rushton of Fibria, Duncan Mayes of Stora Enso and Alex Berg of University of Concepcion joined moderator John Kettle of LUKE. The panel covered a lot of ground:
  • n Key issues in moving to better use of wood start with the kraft process, where recovering cooking chemicals requires burning close to half the wood. A radical new approach to pulping is needed to liberate lignin for higher value-added uses, while continuing to preserve kraft pulp fibre properties. There was, however, little agreement on the best approach, in spite of deep eutectic solvents being the highlight of a recent CEPI study.
  • n A second issue is the need for faster implementation of new processes and products. The pace will be driven by brand owners demanding bio-based functionality. A concurrent approach to R&D – basic, applied and industrial research activities in parallel instead of in series – will be critical.
  • n Breaking biomass down to individual molecules, the way the petroleum industry converts crude oil to aliphatic and aromatic building blocks, will be prohibitive from both financial and ecological perspectives. Trying to reproduce existing petroleum-based molecules will be counter-productive, even if it is chemically feasible. Bringing new molecules to market, however, will be a challenge from a number of perspectives, starting with the regulatory regimes; substitution of existing molecules will come first.
  • n The role of shareholders and financial analysts in impeding or accelerating innovation was discussed. Sharing risk across partnerships, and ensuring that innovation brings new shareholder value, will ensure new investments continue to flow. Ensuring sufficient human resources to deliver knowledge is also critical.

The panel agreed that this is a very exciting time for young researchers to be entering this industry, which is building whole new chemistries, processes for implementing them, and new product streams building on them. A key message for R&D providers was that re-visiting existing ground may be safe, but risks need to be taken.

Representatives from St1, Stora Enso, Metsä Spring and Valmet participated in a panel hosted by Jussi Manninen of VTT. Today the forest industry is profitable in the EU generally, and in Finland specifically, and so is in good position to innovate.

Customer’s viewpoints

Heidi Turunen of Aalto University described architectural use of new materials. This presentation was quite different from the others and provided a fascinating view of the needs of the architectural community, highlighting areas where these needs might not be obvious today to researchers in the novel bio-products field. Technical characteristics of novel materials, such as strength, are important, but appearance and end-of-life issues are also important. Tolerance to water and cleaning products, and ease of repair or replacement, are also key issues when considering architectural elements which remain visible. The key message: understanding the customer (architects, in this case) remains critical. See for more details.

Technical sessions

Deep eutectic solvents (DES)

Given the results of the CEPI Two Team project, it is worth reviewing progress on the topic of DES. This novel pulping technology holds huge promise but is a long way from commercial reality.

DES recovery and reuse systems will be important, and will need to be able to remove water, impurities and process elements like lignin. Two presentations from Lappeenranta University of Technology described use of membrane recovery of DES. Mari Kallioinen described a number of challenges. First, materials used in membranes must withstand DES. Membrane regeneration will also be needed; in an initial trial, membranes recovered 60% of lignin from virgin DES, versus only 32% from reused DES. Finally, a hybrid system including membranes, adsorption and evaporation will be needed to fully remove water. Ikenna Anugworm outlined the potential of DES-generated lignins to foul materials typically used in ultrafiltration membranes. The hydrophobicity of polyethersulfone, for instance, is a useful characteristic in separations processes but makes it more susceptible to fouling. Altering this through addition of hydrophilic functional groups, such as lignin, would reduce this tendency if the DES does not tend to remove the lignin from the membrane. Initial results are promising but work remains.

While not strictly related to DES, a discussion of the impact of wood chip size on the impregnation of wood chips by Jessica Gard Timmerfors of Umeå University is relevant as novel pulping processes are evaluated. Alcaline pulping requires long chips (in order to maintain fibre length) with a consistent thickness (to ensure even impregnation), but acidic pulping is characterised by faster impregnation through the fibre length; furthermore, the importance of fibre length is less in biorefinery applications. Shorter chips are thus of interest. The impact of chipper design and operation on chip dimensions is thus critical and has been evaluated. Impregnation studies are underway. It is worth suggesting that material size reduction to improve contact with a chemical or enzyme, where fibre length is not an issue, can be as cheap and brutal as needed to get the required surface area. Other approaches, such as grinding, may well be adequate as well as cheaper. 

Other solvent pulping approaches

Organosolv pulping has been known for some time, but is not currently in commercial operation. Arguably solvent recovery is one of the bigger challenges, along with obtaining sufficient value from lignin to justify the plant. The same comment can be made for other solvents, such as acetone.
While it is unlikely that acetone will be a common solvent in the forest sector, due to cost and safety issues, the presentation of Anna-Stiina Jääskelainen of Kemira is worth reviewing. She described work done at VTT on acetone fractionation of kraft lignin into three fractions, each different and more homogenous than the feed. The insoluble fraction, extracted at 55% acetone concentration, was removed first and has high MW and low odor, along with low phenolic and carboxylic acid moieties. At 30% acetone, another fraction is precipitated, with low ash and a narrow MWD. The final fraction is soluble and has low MW, low Tg, and high phenolic and carboxylic acid moieties. A process flow chart involving three filter presses and two evaporators for acetone recovery was designed and the techno-economics were evaluated. (These evaporators were not tested in practice). Production costs were €800 (integrated with a pulp mill) to €870 (standalone) per tonne, assuming lignin prices of €461 (wet) and €512 (dry) per tonne entering the fractionation plant. Acetone makeup was the largest operating cost. Capex was estimated in the €40-50 million range for a 50 kt/y plant. The final plant needs to be designed with end-product in mind, as lignin properties will vary depending on conditions. Other presentations on the general topic of acetone extraction are reviewed in the Appendix.

Lignin products and processes

There are now three commercial kraft lignin plants world-wide, using two different technologies. Customers can no longer complain of a lack of lignin suppliers. Some product pathways are close to reality, others more speculative, but the mix shows we are moving to a new phase of improving existing applications, as well as developing new ones. However, few presenters addressed the likely cost implications of additional treatment stages, on top of the basic cost of extracting lignin from wood. The large number of PhD students working in the field is encouraging. Some highlights follow.

A healthy lignin market will require sturdy and well-documented characterisation processes and standards. In this context, Jerk Rönnols of RISE described moving from lab understanding to industrial application with support from analytical approaches. One interesting note was the new availability of simple bench-top NMR units, such as the Magritek Spinsolve 60. While this is unlikely to be suitable as a process or quality control device, research labs associated with producers will be interested in this capability as the market develops. To be followed closely.

The chemical industry requires, or perhaps expects, monomers with purity levels exceeding 99%. This may take some effort, and arguably goes against the comments by James Clark to the effect that we need to build new chemistries around the oxygenated molecules provided by biology, rather than the hydrocarbons available in crude oil. However, there remains a strong push to develop depolymerization processes that could lead to monomers. In that context, Viviana Polizzi of Biorizon and VITO compared methods for recovery of monomeric lignin derivatives from lignin oil. The Biorizon goal is commercial bio-aromatics by 2025. It is hoped to move from a current TRL 3 to TRL 5-6 by 2022. Two streams follow from depolymerization and fractionation of spent liquors and lignin oils: an oligomer mix, and a monomer mix. A catalytic depolymerization process is used, using supercritical ethanol with CuMgAlOx catalyst. A cascade membrane process is used to remove three fractions: Oligomers, dimers and monomers. Other separation techniques yield different fractions. Further chemical modification can add functionalities for more reactivity. Epoxy resins are an example of potential end-products. While the processes described are likely to add significant costs to the base cost of extracting lignin, a proposal for a €4.8M demo in the Port of Antwerp 20-50 kt/y was approved by the EU and a final decision to build is imminent. A mobile 250 kg/d separations pilot for bio-aromatics is also being developed. Separately the BAFTA project developed a database of technical, economic and environmental characteristics for lignins created by over 150 processes. Type of catalyst, solvent, lignin type, T, P, pH and other parameters are taken from the literature and are listed. The engineering firm Jacobs has looked through this to determine which paths will be easiest to scale up, and how best to do so; this exercise will inform the pilot plant design.

Several presenters described enzymatic approaches to modifying lignins. Xihua Hu from the University of Hamburg discussed enzymatic modifications of hydrothermal lignins. The process for lignin extraction was a hot water treatment, with a supercritical fluid extraction stage. An enzymatic stage involving laccases helped couple phenolic molecules to the lignin substrate. Use in several applications such as rubbers were claimed to be economically sensible, although some modification stages added significant cost. Laccase pretreatment was also used to reduce lignin-induced fouling of membrane filtration systems used to purify birch hot water extracts, as described by Tiina Virtanen of Lappeenranta University of Technology. The process joins other tools for maintaining membranes developed at LUT. Gibson Nyanhongo of University of Natural Resources and Life Sciences described using lignin as a binder in pigment-based coating formulations. Lignin modifications are based on a laccase polymerised lignosulfonate. Partial replacement of styrene-butadiene latex formulations was feasible in terms of picking and linting during printing tests, although brightness remains an issue.

Ralph Lehnen of Thünen Institute of Wood Research described functionalization of lignin and hemicellulose using cyclic organic carbonates. Oxyalkylated lignins, using ethylene carbonate or similar solvents, can serve to improve lignin polyols for use in polyurethanes. Xylans can also be etherified by a similar process.

Anna Kalliola of VTT outlined the use of LigniOx lignins in plasticizers and dispersants. The LigniOx process converts lignin to a water-soluble form using an alkaline oxygenation approach, and produces lignins with reduced phenolic OH groups and increased carboxylic groups. Performance in concrete plasticizers can be as good as commercial superplasticizers. It also worked well as a dispersant for calcium carbonate, titanium dioxide and other pigments such as carbon black, as long as the right conditions are selected. Competition with existing lignosulphonate suppliers could limit these applications, however. A mobile demonstration unit is in planning, in partnership with chemical industry and forestry players.

Mohan Kalyan Konduri of FPInnovations described modified kraft lignins for use as dispersants and flocculants, done while the presenter was a graduate student at Lakehead University. A range of modification technologies have been tried and appropriate conditions for dispersants and flocculants have been identified. For dispersants, sulfomethylation approaches worked as well as lignosulfonates or other competing solutions, and were water-soluble at neutral pH. For flocculants, an approach to grafting lignin to an existing polymer worked well in terms of improved turbidity of a clay suspension. By replacing a portion of the synthetic flocculant, cost can be reduced significantly even after accounting for the cost of modifying the lignin. The high cost of existing flocculants, for instance poly-DADMAC, makes this an interesting approach as there is a fair bit of room between the base price of kraft lignin and the cost of these specialised polymers.

Mikhail Balakshin of Aalto University outlined recent advancements in valorisation of technical lignins. The conclusion is that each lignin will find its own niche, with the biomass source and technical processing steps each contributing to defining specific properties and therefore niche markets. This will be true especially in biorefineries based on cellulose to sugar processes where the economics are poor unless lignin revenues are sufficiently high.

Sverker Danielsson of RISE described carbon fibres made by melt-spinning softwood kraft lignin. The target price for carbon fibre in the automotive industry is $11 to $15 per kg, which requires a much cheaper precursor than the poly-acrylonitrile (PAN) used today. High purity lignin is the first step followed by electrospinning or melt spinning, depending on the product. Softwood kraft black liquor was fractionated in ultrafiltration stages with two different molecular weight cutoffs. Carbon fibres with greater than 90% carbon were obtained. Melt-spun fibres can be made with good strength, although PAN remains better. Electro-spun fibre can be made for batteries and supercapacitors with good performance, without the requirements for high tensile strength in traditional carbon fibre applications. While it is reassuring to see applications where strength is not an issue, the question of what is the uppper price limit for ‘high-purity lignin’ in order to get CF at $11 to $15 per kg was not addressed, only that it needs to be ‘much cheaper’ than PAN.

Bark treatment

Several presenters discussed variations on the classic alkaline hot water extraction processes for extracting value-added chemicals from bark; all assumed the residual bark would be used for energy generation, but none considered the impact of a salt-laden, wet bark stream on boiler operation. This needs to be addressed since the economics usually assume that residual bark has the same energy value as the feed, an assumption that is unlikely to be correct. A quick summary of some papers follows.

Pierre-Yves Pontalier of University of Toulouse focused on recovery of phenolic compounds from chestnut trees, which provide a unique challenge due to high tannin and phenolic content. Sami Alakurtti of VTT described extracting polyphenols for use in phenol-formaldehyde adhesives; costs were estimated to be higher than for kraft lignin. Alex Berg discussed using ethyl acetate as a solvent. The range of products were of very high value, although with very low demand. Olumoye Ajao of Natural Resources Canada described a bark-based composite made using a pelletised mix of polypropylene and ground bark; operating costs were a strong function of PP costs.

Thermo-chemical approaches

Hans Heeres of BTG described the Bio4Products process applied to bark. Unlike other approaches to bark, the process is fast pyrolysis followed by a proprietary bio-oil fractionation stage to separate pyrolytic lignin and sugars. Lignin was evaluated in roofing membranes and phenolic resins; sugars were evaluated for use in wood preservatives and furanic foundry resins. Twenty-five million litres of oil were made in a demo plant on the AkzoNobel site in Hengelo, The Netherlands, and largely used as a substitute for natural gas in boilers operated by local industry; the fractionation process is still only at the pilot scale. Pyrolytic lignin is more reactive than kraft lignin but less than petroleum-based resins; it is not ideal for roofing materials at high substitution rates, at least in the type of membrane application tested. However trials in PF resins were more successful at 50% substitution, with a strength loss of about 10% at that rate; this is similar to other lignin-based substitution rates. In PF foam applications, the samples were effective at rates up to 30%. A larger fractionation pilot plant is now necessary and is in commissioning.

Thomas Bräck of Meva Energy described fossil-free fuels in industrial dryers, with a focus on replacing LPG in tissue drying. The process used is an entrained-flow gasification technology, and is online in a CHP plant in Piteå, Sweden, producing 1.2 MW power and 2.4 MW heat. Gas quality is meant to be only as high as necessary for the application. As tissue drying is a direct contact process, a clean flame and reasonably high calorific value fuel is critical. Results of experimental work show this application is feasible.

Peter Axegård from C-Green described biosludge carbonisation. The pilot of 1 t/d is in Örnsköldsvik and a full-scale plant will be built at the Heinola mill operated by Stora Enso, to run on both municipal and paper mill sludges. The process is a hydrothermal carbonisation (wet pyrolysis) step that generates a low-odour ‘bio-coal’ of about 65% carbon by weight. It runs on wet biomass, with a residence time of about 1 hour. Energy required is said to be substantially less than that required for drying of sludge. Organic components in the product stream become hydrophobic and separate from water, making it easy to dewater.  Co-products include an oxidised filtrate which can go back to effluent treatment, and a gas for further treatment. Sludge at 15% solids becomes bio-coal at 55% solids.

Sennai Mesfun of RISE described alternatives for bio-oil production. Most growth in bio-fuels used in Sweden have come from offshore, for instance Asian palm oil biorefineries. Furthermore, low hydrogen contents present a challenge. Production costs for transportation fuel components from forest residues range from €0.60 (hydrothermal liquefaction) to €0.90 per litre (fast pyrolysis). Carbon efficiency is also higher for HTL at 65%, although the TRL for this technology is lower and uncertainties around results are higher. Hydrogen alternatives to steam reforming of natural gas include electrolysis driven by renewable power, and gasification approaches. Both are sensitive to the relative prices and emission factors for power and gas. This field remains one where the difference between biomass price at the gate, and the effective price of crude, is critical. The effective price of crude can be altered by policy initiatives; one study by Don Roberts a few years ago concluded that policy support for use of pyrolysis oil as a replacement for bunker C in US boilers meant the effective price of crude was in the range of $120 to $150 per barrel. With biomass at $100/dry tonne, and oil at $80 to $100/bbl, the economics of biofuels are poor.

Sugar pathways to chemicals

Annelie Jongerius of Avantium discussed their technology for 2nd generation sugars and lignin. The so-called Dawn technology is a process making a pure C6 sugar, a mixed C5/C6 stream, and lignin. The basic Bergius-Rheinau concentrated HCl process is not new, but Avantium has brought some improvements, mainly in acid recovery and lignin drying. Scaleup plans include licensing the technology. The presentation focused on the properties of the lignin produced. Some data is still not available, partly due to poor solubility at room temperature, but it is known that the ash content is low. No comparison to kraft lignin was available. The use of highly concentrated hydrochloric acid remains a deterrent, from the perspective of health, safety and spill control.

Amélie Drouault of Arbiom described a process for producing protein-rich ingredients for food and feed applications from wood. The platform creates 5 and 6 carbon sugar streams. These are suitable for yeast fermentation to a protein-rich ingredient called SylPro. Regulatory approval has been obtained and pilot runs on hardwoods have been completed. The product development program includes animal trials and other industry-specific tests. Markets addressed are aquaculture ($2.5B), weaning pigs ($5.5B) and companion animal ($75B). Fish meal and soy protein concentrates are typical competing products at similar costs. Commercial operation is expected by 2022. These are large markets, and while they are highly segmented and well regulated, partnership with the right player in the field could well be profitable.

Simo Ellilä of VTT described sugar-based cellulase production for on-site production of enzymes. Using the NREL biorefinery model, enzyme costs of $0.06/litre of ethanol were estimated.

Sulfite processes and viscose

Oskar Bengtsson described recent developments at Borregaard. The product mix starts with the unique characteristics of the sulphite dissolving pulp mills. Ethanol purity is increased with a new dehydration plant. Cellulose fibrils are a new product line, with products for industrial and food applications. This is nano/micro-fibrillated cellulose (NFC/MFC), compared to crystalline nano-cellulose (CNC, also called NCC). Focus is on rheology modifiers and barrier films. The BALI process is also in development to generate sugar (from cellulose) and lignin; glucose contents of 90% to 95% are possible. Profitability is said to be good at current 2G ethanol prices. These approaches are, of course, unique to the sulfite platform.

Marc Borrega of VTT described production of viscose-grade pulp and xylan from hardwood kraft pulp. World demand for viscose pulps has doubled since 2008, to close to 10 million t/y. Many conversions of existing kraft mills have taken place. A cheap retrofit approach, combined with the potential to swing back to kraft pulp if needed, is offset by low yields and poor recovery of C5 sugars. Kraft pulp post-hydrolysis (KPH) is one alternative: water-based hydrolysis of BHKP at 240 degrees for up to 10 minutes gives a good removal of a high-purity, high molar mass xylan and significantly higher cellulose yields, but lower pulp viscosity. The cost penalty the market will require in order to accept lower performance remains to be seen.

Raghu Deshpande of MoRe Research described studies on lignin carbohydrate complexes in sulfite pulps. The covalent bonds linking lignin and carbohydrates contribute to properties of trees and wood, and are broken up in different ways in different pulping processes. Studies of lignin content at different cooking times were performed.

Biomass sources other than from timber

Agnieszka Brandt-Talbot of Imperial College London and Chrysalix Technologies talked about Ionic liquids and pathways to a low-cost approach. Specific approaches to deal with so-called waste wood, i.e. construction and demolition residues, were discussed. High levels of contamination are a critical issue in these streams. The BioFlex process uses ionic liquids to extract cellulose and lignin as well as heavy metals. As the raw material is probably a candidate for landfill otherwise, with fees assumed to be 25 pounds sterling, a more expensive process may be acceptable than when the raw material has a price associated with it. That being said, most ionic liquids are very expensive, and recovery is challenging. The process described is said to be very cheap compared to traditional approaches to making ionic liquids, and the type of IL is said to be very easily recoverable.

Marko Snellman, standing in for Ville Vauhkonen of UPM-Kymmene, described using the UPM BioVerno bio-diesel, which is based on crude tall oil, in a range of engine and fleet tests. The process involves a hydrogenation stage and is not a fatty acid methyl ester process. The plant at Lappeenranta, which cost 180 million euros, produces 120 million litres of fuel annually. Next: a plant making 500,000 t/y biofuels from solid wood and brassica carinata, a variant of rapeseed currently cultivated in Uruguay, using solid biomass conversion via hydrotreatment. The plant would be at the UPM mill at Kotka. An investment decision will be made in a year or two.

Appendix: Other presentations

These presentations are described in the interest of providing a complete picture of the conference.

Bernard de Galembert, CEPI, discussed de-fossilizing the economy. The recent report from IPCC, Global Warming of 1.5 degrees, is the basis for discussion. The circular bioeconomy is likely a part of the solution, including the concept of carbon emissions which are in balance with growth of carbon sinks in the form of trees and other vegetation. He also described the paper industry 2050 roadmap.

Matleena Kniivilä of LUKE discussed global megatrends. Key drivers identified included population growth and where it is happening; shifts in economic power and changes in demand for products; impact of climate change on forests and their status as a carbon sink; shrinking resource availability; and balancing different uses of the forests. All are important drivers and it is unclear how these constraints will interact in the future.

Tina Koljonen of VTT (replacing Antti Arasto) discussed Finnish government objectives, based on a range of scenarios which were identified and published by VTT in a report. This can be found online. Other presentations covered more detailed analyses, but in most cases the results are strongly dependent on assumptions around future conditions and may well be proven false if unexpected conditions prevail.

Eirik Ogner Jastad (Norwegian University of Life Sciences) described modeling policy schemes for increasing biofuel use in Nordic countries. Mixed integer linear programming methods took in 29 different products, and tried to maximise consumer and producer surpluses under different scenarios. There were a lot of assumptions covered and conclusions will be changeable depending on these, but it seems that 20% substitution of fossil fuels is possible without major impacts on the existing pulp and paper industry, although at a cost of 5 to 6.5 billion euros.

Florian Gattermayr of Kompetenzzentrum Holz described butanol production from a multi-feedstock stream, i.e. one that includes wood and agricultural biomass. An ABE process was used. This graduate research project is a work in progress.

Frédéric Clerc of EnVertis Consulting described strategies for large-scale production of drop-in biofuels, defined as plants with feeds of 1000 to 2000 odt/d producing 100 to 300 ML/y of biofuels. Growth will be in diesel, jet and marine fuels. Capital costs, mandates and subsidies, yields and returns on investment are among the key risks, which can be mitigated to a certain extent with appropriate partnerships with oil companies or others. 

Fredrik Aldaeus of RISE described the RISE bioeconomy research program for 2018-2020. This is a multi-client project covering a wide range of projects, from cellulose to lignin and from traditional pulping to novel bio-products. Test methods are also in development, as part of an ISO working group from Canada, Finland, Sweden and other countries.

Zoheb Karim of MoRe Research described manufacture of MFC-reinforced nanopaper using a pilot-scale paper machine. First-pass retention versus dewatering time is a critical issue in putting nano or micro-scale materials into a traditional paper machine wet end. As MFC content in the headbox is increased, grammage and drainage both drop due to losses to the white water system. Mixing MFC with pulp fibres prior to the headbox was one approach to retaining MFC; another is addition of cationic starch and silica microparticles. Maximum MC retention was about 67%, with total retention of fibre + MFC of about 85%.

Mihaela Tanase-Opedal of RISE PFI described a novel reactor for an acid-catalysed organosolv saccharification pre-treatment stage, with the objective of increased enzymatic accessibility. Acetone with water at a mass ratio of 1:1 is the solvent used. The feed was Norway spruce. Increasing cellulose accessibility is more important than delignification for fast release of sugars. Reactor design can assist in this. Compared to conventional autoclave-type reactors, the novel reactor has short heat-up time, high temperature capabilities, good mixing and the ability to displace and exchange cooking liquid during a run. In enzymatic hydrolysis, 99% cellulose conversion in 24h was possible, even with 28% lignin, at 31 mg protein per g. (Lignin content is due to re-precipitation onto cellulose fibres).

Eero Kontturi of Aalto University described degradation of cellulose by HCl gas at high pressure in a novel reactor, for CNC production. Sulfuric acid is the conventional approach but an approach using dry HCl gas can work well at room temperature, with yields of 97%. Gas can be easily recovered, but dispersion of CNC from hydrolysed fibres can be challenging.

Raimo van der Linden of BPF described challenges in scaling up lignocellulosic pretreatment technologies. Technical and market validation require piloting, which cost money but do not earn revenues. “Scale down” what the commercial process might look like, not “scale up” the bench unit operations. BPF has a range of equipment available covering pretreatment, fermentation and downstream processing as well as a food-grade lab. Continuous processes are challenging but necessary.

Olumoyo Ajao of Natural Resources Canada described lignin solubility in solvents and polymers. Solubility is a challenge for lignin valorisation. Quantifying solubility can be undertaken with Hansen Solubility Parameters. Dispersion forces, Polar/dipolar interactions and Hydrogen bonds are used to calculate an overall total solubility parameter. Forty different lignin types (source and processing type) in 250 mg samples were mixed with 20 different solvents, and solubility was evaluated visually. (Full quantitative determination of solubility parameters is time-consuming and has only been done for a few samples.) This visual evaluation was  used as a basis for estimating Hansen solubility parameters for lignins in a range of solvents, including mixes of solvents. Acetone and water at a ratio of 72:28 are best suited to kraft lignin. In the second part of the study, compatibility of kraft lignin with a range of polymers was evaluated. The points where the Hansen solubility radii for lignin and the specific polymer overlap is a good indication of compatibility. The compatibilizer selected acts as a bridge, and a shorter distance between Hansen solubility radii is better.

Jari Heinonen of Lappeenranta University of Technology described extracting hydroxy-carboxylic acids, which represent 20% of the dry solids in kraft cooking liquors. Separation is challenging. Chromatography and ion exchange has been tried. Lignin and NaOH can also be recovered from liquor and from hydroxy-carboxylic acids. Markets for these acids are still not understood.

Lauri Pehu-Lehtonen of Andritz described the A-Recovery+ technology for chemical recovery. This includes methanol purification and recovery; sulfuric acid recovery from CNCGs in a process developed with Haldor Topsoe; and lignin recovery using a proprietary process based on expired patents. Methanol can be used in the ClO2 generator or sold; sulfur can be used internally or sold; and lignin can be used to displace fossil fuel in the lime kiln or sold. Simple payback can be under 3 years depending on use of the various streams being extracted. Five thousand tonnes per year of biomethanol will be generated at Södra Cell Mönsteras by Q3 2019. 

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