Hardwood from Softwood

A great divide separates the broad-leaf trees that produce hardwoods, and the conifers that produce softwoods. Conifers, such as pinus radiata, grow quickly and are suited to commercial production. Hardwoods, on the other hand, grow slowly, some taking centuries to mature; but their timber is beautiful and durable, and commands a premium. A single teak log can fetch $40,000. Alistair MacKenzie looks into the process that Forest Research scientists have devised to bridge the divide and rescue pinus radiata from its Cinderella status.

Seventeen years ago, scientists at what was then the Forest Research Institute (now a Crown Owned Research Institute called Forest Research) asked themselves how they might lift the value of New Zealand's softwood crop (conceptual statement).

They had raised pine silviculture to a high art. They had developed cultivars ideally suited to the timber industry. They had learned to space trees so they competed with each other and grew straight and tall, and to make trees grow more quickly. They knew how to manage tree pests and diseases, and how and when to harvest timber to maximise yield. They recognised that the key to raising the value of pine still further lay in adding value after harvesting. Using pinus radiata as their base material, they set about the alchemy of turning softwood into hard.

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The Inside Story

Wood is a wondrous material – its stability, load-bearing capacity and convenience make it the most efficient structural material known. These properties do not derive from the constituent materials, but rather from their arrangement. Wood is composed of parallel columns of long hollow cells (fibres) joined end to end, their walls forming the load-bearing shell of the cells and of the whole plant.

The cell walls in a living tree consist of fibrous sheets laid across each other, like plywood. A helical criss-cross arrangement of fibres in adjacent layers gives the assembly toughness and strength. Each layer is a composite of cellulose crystalline fibres in a resinous matrix of organic polymers – lignin, hemicelluloses and non-crystalline cellulose. The fibres confer strength, while the matrix gives the sheet lateral stiffness and transfers stress from fibre to fibre, improving toughness.

The toughness of wood, as calculated from the theory of fibres in a resin matrix, is only one tenth of that actually observed. Toughness is largely about managing the fracture process, which wood does to perfection. Cracks are encouraged to wander around within the material, without being allowed to go right through it, more or less harmlessly using up the available strain energy.

A dry piece of wood consists of a rigid foam, an empty lattice of cell walls. The thickness of the walls determines the density of the wood and so its mechanical properties: balsa wood has thin cell walls, while the cells walls of lignum vitae, one of the densest woods, are so thick they almost occlude the cell cavity.

The Product

A standard sawmill can be retrofitted for the process in about six months, for around $800,000. Figures published last year suggest the process increases the value of softwood timber from around $320 to around $1880 per cubic metre.

Indurite-hardened pine has improved fire retardancy, and is 35 percent less responsive to changes in moisture content than untreated pine; and its strength, both in terms of elasticity and rupture, is better by 30 percent. This combination of qualities makes the treated timber ideal for flooring. Floorboards can be thin and wide, and while they are as dense as hardwood boards, they are stiffer, don't splinter and have good screw-holding characteristics, which makes them easier to lay.

In 2001, the FRI sold the patent for the process to Waiuku-based Engineered Wood Solutions. EWS's UK distributor, Nu Wood, has fitted more than 300 indurite floors to properties including more than 40 London apartments.

While flooring is the main market for Indurite timber, the potential for replacing expensive hardwoods in other applications is enormous. Fully 90 percent of the world's writing instruments are pencils; their sharpened points must be firmly supported, and so they are made from hardwoods. The amount of wood in one pencil isn't huge, but the cumulative market is; Euro Business magazine reported last year that EWS was in talks with one of the world's pencil giants about replacing hardwoods with Indurite-treated pine. Similarly, the handles on paintbrushes – another enormous market – are conventionally made from hardwoods.

The Age of Biopolymers?

This century has been named the Age of Materials. It's likely technology will advance by improving materials of all types. Metallic materials and non-metallic materials – plastics, ceramics, glass, carbon fibre – will be used increasingly in mixtures, and composites. The ingredients for combination will include biological materials, and among them wood and its constituents.

Over the past century, synthetic polymers such as nylon and polyethylene and have become ubiquitous, reliance on them is being questioned. Most plastics are derived from non-renewable resources and are not biodegradeable. The very durability and strength that makes them so useful ensures their persistence in the environment and complicates their disposal. The synthesis of some materials also involves toxic compounds or the generation of toxic by-products. These concerns have turned attention to bio-polymers.

Bio-polymers are a class of diverse "giant" molecules, consisting of discrete building blocks (monomers) linked into chains. Proteins are biopolymers, and so are polysaccharides such as starch and cellulose. Derived from biological precursors or produced using biotechnology, bio-polymers have a huge range of potential applications, including adhesives, absorbents, lubricants, textiles, and high-strength materials. While many potential applications are still in the developmental stage, some have already emerged in the packaging, food production and medical fields.

Because they are biodegradable, bio-polymers may reduce waste to landfills or incinerators. They may also permit more environmentally benign manufacturing processes. Producing many advanced materials involves energy-hungry processes that create or require toxic substances. Living organisms, on the other hand, can produce sophisticated materials under low temperature and pressure without creating toxic by-products. Spiders, for example, can transform water-soluble protein droplets into an insoluble web using very little energy.

(Some bio-polymers may also replace synthetics, reducing the use of petro-chemicals, but it is easy to overstate the case. In the USA, about 15 percent of all materials used for commercial purposes are derived from petroleum, but only 3 percent of petroleum supplies are used to produce petrochemicals and synthetic resins. The substitution of biopolymers would not by itself significantly affect oil consumption.)

By harnessing enzymes found in nature or by transforming agricultural or marine feedstocks, a new class of biodegradeable, biocompatible and renewable material may be created. And it's on this vision that Forest Research has hung its hopes. Late last year, it announced a radical shift, away from its traditional focus on forestry and wood processing, towards creating "totally new value chains" from biomaterials – non-food materials derived from plants.

New vision, new venture

Using government funding as venture capital, Forest Research is focussing on the areas of science that underpin advances in biomaterials, and is recruiting specialist staff in key areas such as biotechnology, bioconversion and biomaterials engineering.

Before committing itself to the change, Forest Research spent 18 months considering the social, technological, economic, environmental and political changes likely to occur in the next half-century. After mapping a series of likely scenarios, Forest Research staff set about predicting appropriate technological responses.

Their results confirmed that biomaterials are the way of the future, representing a major opportunity for New Zealand. Forest Research is picking that within a decade, biomaterials will become a major influence in global manufacturing. This shift is being driven by a growing demand for renewable and biodegradable products. Forest Research cites a projection made by the US Office of Industrial Technologies (OIT) that at least 10 percent of basic chemical building blocks will be sourced from plant-derived renewables by 2020, 50 percent by 2050.

This change in direction is also a pragmatic acknowledgement that times have changed for Forest Research. Commercial demand for their traditional capabilities has diminished as the domestic forestry industry has become technologically self-sufficient; and science has become so competitive and technological change so fast, that it is difficult to compete on multiple fronts. Focusing on a niche makes sound commercial sense.

Forest Research has restructured into six business units and three "transformational science platforms" – biotechnology, bioconversion and biomaterials engineering. Of these, bioconversion, which involves processes such as fermentation and the production of bioplastics from waste streams, may become Forest Research's particular niche.

Fixing waste streams

Conventional treatment systems use bacteria to mop up the soluble carbon from waste; but the bacteria must be fed huge quantities of nitrogen and phosphorus fertiliser, much of which escapes into the environment. Consequences include eutrophication of waterways, and remediation costs industry plenty – around $5 billion a year for the pulp and paper industry.

The N-ViroTech system exploits the ability of some bacteria to fix atmospheric nitrogen. These bacteria supplement the diet of the other micro-organisms in the treatment system, reducing the quantity of chemicals discharged by 90 percent. The system may be installed cheaply in existing plant and, once tuned, is essentially self-regulating. A Swedish pulp and paper mill trialled the system earlier this year and four international patents are pending. A system (called N-ViroPol) for extracting economically useful polymers from the treatment systems is under development.

For more information visit Green Seal www.greenseal.co.nz