Report from PulpPaper18 Conference in Helsinki
General Trends of forest resources
The majority of European forests locate between 55th and 70th degrees latitude in Norway , Sweden and Northern Russia. The volume of Finnish forests is continuously growing due to the advanced forest management practises allowing moderate consumption for multiple applications. Thus, the stem volume is presently more than 2350 mill. m3 keeping at the same time 20% of forests in restricted use or outside the commercial use. The annual growth of Finnish forests reached 105 mill. m3 (4,5%), generated mainly (85%) by the areas without any restrictions of use. The present annual cut in 2017 reached 73 mill. m3. In various scenarios of Luke (Luonnonvarakeskus) for a time span of 100 years is has been shown that in case of rising removal to 80 mill. m3, long term intensive forest management is beneficial and volume up to 3500 mill. m3 with a considerable high negative CO2 balance. Digitalization is important for information and planning, for trials of new machine concepts and for monitoring methods (e.g. drones). New technology is needed to overcome the adverse impacts of climate change causing shorter winters and rainfall distribution.
Many European political regulatory instruments are managing wood and nature conservation as well climate change adaptation. These include management of for wood processing, energy value chains and paper/pulp production aiming the broader societal, economic and environmental objectives of EU forest-based bio-economy. There is some incoherence of all these regulations, e.g. sustainability criteria, which still have an influence the potential use of wood and forest biomass in the future.
The novel set of a forest-based biorefinery targets multiple products, such as biomaterials, biochemicals, biofuels and bioenergy. A pioneering biorefining has been developed in Borregaard Norway, where a traditional paper mill was transformed to utilize lignin for energy and chemicals, cellulose for special applications and hemicellulose to produce bioethanol. Lignin-based products include purified lignin, oxylignin- and lignosulphonates and vanillin. From cellulose, special celluloses for viscose and chemical industries, microfibrillar cellulose (nanocellulose) and cellulose sugar are produced. The scope could be enlarged further depending on the overall capacity, wood raw material type and type of cooking process. The pulp-integrated manufacturer (e.g. Lenzing) is able produce acetic acid, furfural, xylose, soda and ashes from hardwood sulphite pulping and sodium sulphate additional to viscose fibers from the fiber plant. Concentrated carbon disulphide gases are recycled (>90%) by means of active carbon, whereas dilute flows are oxidized to sulphuric acid and reused in the viscose process.
The waste material side-streams containing nitrogen, phosphorus and sulphur from biorefineries can be utilized as soil improvment additives in agriculture. Those include slurry from biogas and ethanol, pulp fibers from forest industry, micronutrients from process industry and various additives for soil pH control. This may serve as well as for carbon sequestration and storing it the soil and nutrient recycling, which reduces the amount of ammonia needed to synthetize.
Overall situation in Finland
The Finnish government and a special foundation Sitra support the development of circular economy and development of forest-based loops. Key projects are developing of composite materials, recycling of industrial waste to biocomposites and cross-laminated solid wood elements for buildings. Aditionally, the changes of pulp&paper markets and development of energy, chemicals and textile markets, various new investments and plans are made in Finland. This is increasing the wood demand remarkably, because many of the decided investments (Metsä, UPM, Keitele, etc.) already demand more than 8 mill. m3/a more of wood. Coming investments in Kemijärvi (Boreal Bioref), Kajaani (KajCell) and Kuopio (Finnpulp) plus others may increase the demand by further 8 mill. m3/a.
Metsä Group´s biorefinery produces, beside of pulp, tall oil and turpentine, sulphuric acid, biogas (methane), electricity and bark. In the piloting stage are new textile fibers (ionic liquids) and biocomposites from pulp.
Additional to process control and automatization, digitalization is showing widespread applications in supply chains, robotics, machine learning, virtual reality, cyber security and materials technology. Virtual planning and simulation will be increasingly used instead/before of real world operations, e.g. planning of forest cuts and their transportation logistics and waste water treatment. In industrial maintenance, the machinery and assets, their current information status and service instructions can be easily evaluated. In practical maintenance, inspection, visualization, instructions are used targeting the whole responsible action group at the same time.
Due to the production of carbon dioxide-aware energy biofuels have been realized as an important part of modern biorefineries. Side-streams of mechanical and chemical forest industry, such as saw dust, cellulosic-based waste and residues in and black liquor of kraft pulping are used as raw materials for biofuels. St1 started ethanol plants using forest industry residues in year 2006 in Norway and later included food processing residues as raw materials and modified lignin for diesel and jet fuel production. The biofuel production scheme in Kajaani include thermal treatment, hydrolysis, fermentation, distillation and dehydration stages. Additional to ethanol, turpentine and furfural is produced.
Fortum has increased the share of biomass in power (2%) and specially in heat production (22%). The bio-oil is produced with fast pyrolysis technique under oxygen free conditions. The bio-oil contains several hundreds of different molecules including water, shows a low pH value and has a heating value about half of mineral oil.
Renewable UPM bio-fuels are made in Kaukas Finland from the residual tall oil from chemical pulping by a hydrotreatment and fractionating processes, which ensure the removal of sulphur and overall purity. The products are pure hydrocarbons with physical and chemical properties that match fossil diesel fuel and a naphta oil (high hexadecane/cetane number), which can be used as a biocomponent in fossil gasoline.
The existing utilized side-products generated by the production of sulphite pulps are lignosulphonates, vanillin, acetic acid, furfural and xylose. In case of kraft pulping tall oil and turpentine, sulphuric acid, biogas and bark are produced. The black liquor of kraft pulping can be purified and further advanced products can be produced, such as lignin, oxidized lignin, polymer derivatives for glues and resins, carbon and carbon fibers. According to Ligno-Boost process, lignin products are classified as follows: pure lignin for fuels, odor-free lignin for binders, ultrapure lignin for bioplastics and carbon fibers, pure lignin and carbon green for technical carbons, fractionated lignin for carbon fibers and water-soluble lignosulphonate for dispersants.
Nanocellulose is presently classified rather as chemical than fiber, because of the exceptional behaviour compared to textile and pulp fibers. For separating 30-50 nm nanofibril bundles from pulp fibers, large amount of chemical and physical energy is needed. The production of nanocellulose of 3-4 nm of fibril diameter, chemical, chemo-mechanical and enzymatic techniques are used and a gel-like product containing less than 1% cellulose is resulted. The distribution of nanocellulose fibril shape and properties depend on the production method. Similar as polymers, nanofibers show shear thinning rheology in water solution and is capable forming films and fiber-like structures when pumped through small slits or holes.
When used in coating of plasticized paperboard for packaging, nanocellulose can introduce the coverage of 1-11 g/m2, which reduces the air and water vapor permeability by 80-90%. The barrier for grease is approaching zero in 5-6 g/m2 coating and for heptane in 9-16 g/m2 coatings. For more easy processing and resulting uniform coatings, higher solids of nanocellulose gels are needed. Additional to coating, nanocellulose can be applied as reinforcing filler in composites, thickeners in paints, cement and cosmetics, and in oil drilling fluid. Due to its transparency, high modulus and flexibility, nanocellulose can be utilized as a layer for constructing optical OLED cover windows.
When using phosphorylated pulp containing 0,3 – 1,2 % of phosphorus in the production of nanocellulose, the properties of thickeners are improved. The tensile strength of the P-nanocellulose film is higher compared with ordinary nanocellulose. It can also be used for reinforcing element in polycarbonate films.
Wood fibers for textiles
Textiles is an important group of consumables, and currently, more than 65 % of the fibres produced globally are synthetic man-made fibres, 34 % are cellulose-based fibres including cotton and man-made cellulosic fibres, and the rest consists of wool and other natural fibres (CIRFS 2015). The advantages of the cellulosic fibres over the synthetic oil-based fibres are their high hydrophilicity and breathability, comfortable touch, biodegradability, biocompatibility and the use of renewable resources. Cotton fibres cover the major part (89.5 % in 2011) of the textiles made from the cellulose-based fibres. Following the trend, it is estimated that the fibre consumption exceeds 15.5 kg per capita by 2030 with the global fibre production of 135.4 million tons (90 mill. tons in 2016). The production of synthetic fibres has increased dramatically since the end of 1990’s and seems currently to response the best for the total fibre demand. The production of cotton has fluctuated from year to year and has increased only moderately. After a steady decrease since the mid 1970’s, the production of man-made cellulosic fibres has started to increase during the past ten years reaching more than 6 mill. tons in 2017.
The increased demand of viscose (cellulosis) fibers has resulted in growing investments and plans of new capacities, mainly in China and South-East Asia. According to the announcements of leading viscose producers, a further 1-2 mill. annual ton is being builded during 2020´s. In many countries, including Finland, there are new processes developed for production of cellulose (viscose) fibers by using solvent or water-based alkaline methods. This has been motivated pulp manufacturers to add their capacities by rebuilding paper pulp processes to dissolving and to build new capacities specially since 2011 to 2019 in China, South Afica, Chile, Thailand, Laos, Indonesia, Sweden and Finland. The quality requirements for dissolving pulp include purity and low variation, high alpha cellulose content, adjusted polymerization degree (DP, PD), low hemicellulose content and high brightness. Main processes are prehydrolysed kraft pulping and sulphite pulping. Further purity and separation of chemicals (e.g. MCC in Kajcell and xylans) can be reached by novel autohydrolysis processes before or after cooking.
Some novel approaches in Finland aim to utilize recycled cardboard or fine paper and cotton as a raw material for regenerated cellulose fibers. The first one is based on ionic liquids, which are capable for dissolving various cellulose sources. The second one utilizes waste cotton, e.g. blue jeans by deinking and thermal treatment to cellulose carbamate. In both cases, the preliminary results are promising and a pilot plant design for carbamate process is under way.
Bioplastics and new cellulose materials
The environmental problem of plastic waste in oceans, caused by transfer of the local waste along the main rivers of the globe to oceans, has caused much public attention. The consumption of plastics has grown from 1,5 mill. tons in 1950 to 322 mill. tons in 2015, which is more than three times higher compared to textiles. Many brand owners producing consumables have already stated to change their raw-materials from oil-based raw-materials to renewable bio-based materials replacing plastics. Early inventions such as cellulose nitrate 1862 (Parkesine), cellulose acetate/copolymers and celluloid are bio-base polymers, but show only limited biodegradation. Polyhydroxy butyrate plastics invented in 1933 and polylactic acid esters in 1989 are biodegradable with certain bacteria. Cellulose acetate/copolymers have shown many applications, where water or thermal resistance and gas barrier properties are not needed. Poly(butylene succinate) PBS is the most common biodegradable polyester produced by polycondensation.
Among polyesters produced by microbes, poly(hydroxy alkanoates) PHA are biodegradable (also in marine) aliphatic polyesters. They are produced by micro-organisms (like Alcaligenes eutrophus or Bacillus megaterium) using raw materials such as food waste, agro waste, ligno-cellulose biomass even plastic waste and carbon emissions are possible. Some examples are polyhydroxybutyrate (PHB) and –valerate (PHBV) and –hexanoate (PHBH) and their tensile strength and water resistance is close to polypropylene. Starch based biopolymers include thermolastic starch TPS consisting starch, plasticizer and binder (PLA,PVOH, PCL). Largest current plastic applications are compostable waste bags and other bioplastics. They show good biodegradability, but low-medium water resistance.
Polyethylene furanoate (PEF) is 100% biobased (wood-based) polymer to compete with PET. It shows better barrier properties than PET (O2 10x, CO2 4x, H2O 2x better). Replacements for PET, polyamides, polycarbonates and plasticizers are developing depending mainly on the efficiency of furfural synthesis to furanedicarboxylic acid.
Polymers based on biomass could be produced by micro-organisms, by modified biomass or by monomers based on biomass. By modifying the biomass, starch derivatives, cellulose derivatives, hemicellulose products and lignin products have been demonstrated. Surprisingly, many of the common monomers can be produced bio-based. The synthesis route goes through the production of ethanol by fermentation of carbohydrate biomass and reducing it catalytically to ethene followed by the polymerization and necessary modification. Also, wooden chips can be combined with plastics and are available for applications, especially combined with natural resins.
Nanocellulose gel can be converted with hot air to form Cellufoam, which is a low density porous material made of cellulose and Celluspheres which are transparent. Tiny wooden chips can also be combined with bio-based resins or lignin derivatives useful in packaging materials for cosmetics and other consumer products.