Boitechnology

These include copper HDO (CuHDO), copper chromate, copper citrate, acid copper chromate and ammoniacal copper zinc arsenate (ACZA). The CuHDO treatment is an alternative to CCA, ACQ and CA used in Europe and in approval stages for United States and Canada. AZCA is generally used for marine applications.

Alkaline copper quaternary (ACQ) is a preservative made up of copper, a fungicide, and a quaternary ammonium compound (quat), an insecticide which also augments the fungicidal treatment is a wood preservative that has come into wide use in the USA, Europe, Japan and Australia following restrictions on CCA. Its use is governed by national and international standards, which determine the volume of preservative uptake required for a specific timber end use.

Since it contains high levels of copper, ACQ-treated timber is five times more corrosive to common steel, according to American Wood Preservers Association (AWPA) test results. It is necessary to use double-galvanized or stainless steel fasteners in ACQ timber. Use of fasteners meeting or exceeding requirements for ASTM A 153 Class D meet the added requirements for fastener durability. The U.S. began mandating the use of non-arsenic containing wood preservatives for virtually all residential use timber in 2004.

Modern versions have been developed which offer improved performance to those mentioned above. It should be noted that the American Wood Protection Association (AWPA) standards for ACQ require a retention of 0.25 pounds per cubic ft (PCF) for above ground use and .40 pcf for ground contact.

Chemical Specialties, Inc (CSI, now Viance) received US EPA’s Presidential Green Chemistry Challenge Award in 2002 for commercial introduction of ACQ. Its widespread use has eliminated major quantities of arsenic and chromium previously contained in CCA.

An extremely common preservative originally developed in the 1930s at the Forest Research Institute in Dehra Dun, India, by Dr. Sonti Kamesam. Dr Kamesam sold the patent rights for what he originally called ASCU salts to the Bell Telephone Company of the USA. The acronym “CCA” is believed to have come into popular use for this product in the 1950s. In CCA treatment, copper is the primary fungicide, arsenic is a secondary fungicide and an insecticide, and chromium is a fixative which also provides ultraviolet (UV) light resistance. Recognized for the greenish tint it imparts to timber, CCA is a preservative that was extremely common for many decades; however, it contained arsenic.

Pressure treatment with an aqueous solution of CCA salts is often known in the UK, Australia and New Zealand as tanalisation (or tannalisation). The chemicals are applied using a vacuum and pressure cycle, and the treated wood is then stacked to dry (see Application Processes below). During the process, the mixture of salts reacts to form insoluble compounds, helping with leaching problems. If the process is carried out correctly, very little preservative is left on the surface of the wood, and the safety hazard from surface toxins is minimised. Occasionally, a white powdery deposit may be seen on the surface; this is either hydrated-sodium sulphate, a harmless by-product of the CCA salts, or some resin that has exuded from the wood during treatment. Both these deposits are easily removed by scrubbing or brushing, and such treatment will also reduce the minimal amounts of arsenic, which may be present on the surface of the wood.

The process can apply varying amounts of preservative at varying levels of pressure to protect the wood against increasing levels of attack. Increasing protection can be applied (in increasing order of attack and treatment) for: exposure to the atmosphere, implantation within soil, or insertion into a marine environment.

In the last decade concerns were raised that the chemicals may leach from the wood into surrounding soil, resulting in concentrations higher than naturally occurring background levels. A study cited in Forest Products Journal found 12–13% of the chromated copper arsenate leached from treated wood buried in compost during a 12-month period. Once these chemicals have leached from the wood, they are likely to bind to soil particles, especially in soils with clay or soils that are more alkaline than neutral. In the United States the powerful US Consumer Product Safety Commission issued a report in 2002 stating that exposure to arsenic from direct human contact with CCA treated wood may be higher than was previously thought. On 1 January 2004 the Environmental Protection Agency (EPA) in a voluntary agreement with industry began restricting the use of CCA in treated timber in residential and commercial construction, with the exception of shakes and shingles, permanent wood foundations, and certain commercial applications. This was in an effort to reduce the use of arsenic and improve environmental safety, although the EPA were careful to point out that they had not concluded that CCA treated wood structures in service posed an unacceptable risk to the community. The EPA did not call for the removal or dismantling of existing CCA treated wood structures.

In Australia, the Australian Pesticides and Veterinary Medicines Authority (APVMA [1]) restricted the use of CCA preservative for treatment of timber used in certain applications from March 2006. CCA may no longer be used to treat wood used in ‘intimate human contact’ applications such as children’s play equipment, furniture, residential decking and handrailing. Use for low contact residential, commercial and industrial applications remains unrestricted, as does its use in all other situations. The APVMA decision to restrict the use of CCA in Australia was a precautionary measure, even though the report[2] found no evidence that demonstrated CCA treated timber posed unreasonable risks to humans in normal use. Similarly to the US EPA, the APVMA did not recommend dismantling or removal of existing CCA treated wood structures.

In Europe, Directive 2003/2/EC restricts the marketing and use of arsenic, including CCA wood treatment. CCA treated wood is not permitted to be used in residential or domestic constructions. It is permitted for use in various industrial and public works, such as bridges, highway safety fencing, electric power transmission and telecommunications poles.

Timber or lumber that is treated with a preservative generally have it applied through vacuum and/or pressure treatment. The preservatives used to pressure-treat timber are classified as pesticides. Treating timber provides long-term resistance to organisms that cause deterioration. If it is applied correctly, it extends the productive life of timber by five to ten times. If left untreated, wood that is exposed to moisture or soil for sustained periods of time will become weakened by various types of fungi, bacteria or insects.

Chemical preservatives can be classified into three broad categories: Water-borne salts, Oil-borne preservatives, and Light Organic Solvent Preservatives (LOSPs). These are discussed in more detail below.

Old timber industrially treated with approved preservative products pose a limited risk to the public, but should be disposed of properly. On December 31, 2003, the wood treatment industry voluntarily stopped treating residential lumber with Arsenic and Chromium (Chromated Copper Arsenate, CCA). This was a voluntary agreement with the United States Environmental Protection Agency. CCA was replaced by Copper based pesticides, with exceptions for certain industrial uses. [2] Industrial wood preservation chemicals are generally not available directly to the public and may require special approval to import or purchase depending on the product and the jurisdiction where being used. In most countries, industrial wood preservation operations are notifiable industrial activities that require licensing from relevant regulatory authorities such as EPA or equivalent. Reporting and licensing conditions vary widely depending on the particular chemicals used and the country of use.

Although pesticides are used to treat lumber, it’s important to realize that preserving lumber is intended to protect our natural resources saving forestland. Unfortunately previous poor practices in industry have left legacies of contaminated ground and water around wood treatment operation sites in a number of cases. However under currently approved industry practices and regulatory controls such as implemented in Europe, North America, Australia, New Zealand, Japan and elsewhere, environmental impact of these operations should be minimal.

Wood treated with modern preservatives is generally safe to handle given appropriate handling precautions and personal protection measures. However, treated wood may present certain hazards in some circumstances such as during combustion or where loose wood dust particles or other fine toxic residues are generated or where treated wood comes into direct contact with food and agriculture.

Material safety data sheets and safe handling guidelines are required by law to be provided by suppliers of wood preservative chemicals and treated wood products. This information should be obtained and reviewed before handling and using wood preservative chemicals and treated wood products.

All measures that are taken to ensure a long life of wood fall under the definition wood preservation (timber treatment). Apart from structural wood preservation measures, there are a number of different (chemical) preservatives and processes (also known as timber treatment or lumber treatment) that can extend the life of wood, timber, wood structures or engineered wood. These generally increase the durability and resistance from being destroyed by insects or fungus.

As proposed by Richardson,[1] treatment of wood has been practised for almost as long as the use of wood itself. Some accounts reach back to the beginning of recorded history. For example the Bible in Genesis, 6:13-14 “And God said unto Noah… make thee an ark of gopher wood; rooms shalt thou make in the ark, and shalt pitch it within and without with pitch.” There are also records of wood preservation reaching back to ancient Greece during Alexander the Great’s rule, where bridge wood was soaked in olive oil. The Romans protected their ship hulls by brushing the wood with tar. During the Industrial Revolution wood preservation became a corner stone of the wood processing industry. Inventors and scientists such as Bethell, Boucherie, Burnett and Kyan made historic developments in wood preservation, with the preservative solutions and processes.

Pellet stove
Wood pellets
Efficient stove for developing nations
Sawdust can be pelletized

In 2008, wood for fuel cost $15.15 per 1 million BTUs.[19]

Wood heat continues to be used in areas where firewood is abundant. For serious attempts at heating, rather than mere ambiance (open fireplaces), stoves, fireplace inserts, and furnaces are most commonly used today. In rural, forested parts of the U.S., freestanding boilers are increasingly common. They are installed outdoors, some distance from the house, and connected to a heat exchanger in the house using underground piping. The mess of wood, bark, smoke, and ashes is kept outside and the risk of fire is reduced. The boilers are large enough to hold a fire all night, and can burn larger pieces of wood, so that less cutting and splitting is required. There is no need to retrofit a chimney in the house. However, outdoor wood boilers emit more wood smoke and associated pollutants than other wood-burning appliances. This is due to design characteristics such as the water-filled jacket surrounding the firebox, which acts to cool the fire and leads to incomplete combustion. Outdoor wood boilers also typically have short stack heights in comparison to other wood-burning appliances, contributing to ambient levels of particulates at ground level. An alternative that is increasing in popularity are wood gasification boilers, which burn wood at very high efficiencies (85-91%) and can be placed indoors or in an outbuilding.

Wood is still used today for cooking in many places, either in a stove or an open fire. It is also used as a fuel in many industrial processes, including smoking meat and making maple syrup.

As a sustainable energy source, wood fuel also remains viable for generating electricity in areas with easy access to forest products and by-products.