Eco-Friendly Preservation of Woods

The continuous depletion of forests calls for the astute usage of existing resources. Fungie and termites cause serious damage to biomass under storage and service conditions. Various protective treatments with high amounts of toxic chemicals are used by the wood industry trials are being made the world over to development of environmentally friendly preservatives for wood species. Recent research highlights that potential and effectiveness of traditional practices and procedures, mainly water leaching technique and smoke treatment are useful in wood preservation. Under laboratory conditions, the service life of treated blocks were found to be at a par with commercial chemical preservative treated blocks. Various plant extracts and oil-based formulations, such as organic acids, essential oils, and eco-friendly chemical-based preservatives, are in the stage of development. The bio-efficacy of such preservatives is measured in terms of the improvement in resistance to fungi and termites. However, much work still needs to be done to completely determine the efficacy of many of these newly developed preservatives and techniques. The present paper discusses an overview of the developments in the field of environment-friendly biomass preservatives.  

Eco-Friendly Chemicals for Enhancing the Durability of Wood

Eco-Friendly Preservation of Woods

The present paper discusses the latest developments in the techniques of preservative impregnation inside biomass culms. The latest developments in the methods of wood cell wall modification, heat treatment, and supercritical fluid extraction techniques are compiled and discussed. The bio-efficacy of such preservatives is measured in terms of improvement in fungus resistance, termite resistance, and field performance. Rigorous field testing is required to license the recommendation of a technique for a biomass species. The present paper provides an overview of the developments in the field of environment-friendly preservation for wood and bamboo species.

NEED FOR ECO-FRIENDLY PRESERVATION TECHNIQUES

Chemical treatmentsuch as CCA and many others has been considered a solution to enhance the service life of biomass species. The chemicals used by local artisans as well as industry include

1. copper chrome arsenic (CCA),
2. sodium pentachlorophenol,
3. boric acid-borax,
4. Cu/Zn naphenates/ abietates,
5. tebuconazole,
6. IPBC (3-iodo 2- propanyl butyl carbamate),
7. chlorothalonil, isothiozolones,
8. synthetic pyrethroides, 

many  harmful effect of these chemicals has led to their ban in many countries. The leaching of these chemicals into the soil and water has may be carciogenic. Even though biomass culms are treated with CCA, creosote preservatives have been able to extend the service life of wood to around 36 years, yet their toxicity cannot be ignored. The odor of creosote makes it a preservative for outdoor application only. CCA, AAC, and CCB contain arsenic and chromium. The carcinogenicity of chromium and arsenic is a well-known fact. For this reason. PCP is banned for use in most countries.

Looking at the toxic effects of many of these preservatives, researchers are attempting to develop eco-friendly preservatives (Xu et al. 2013). The successful preservation of wood was defined as the safe storage of a large quantity of wood that could later be used.

Good Harvesting Practices

Liese and Kumar (2003) also reported that the harvesting time affects the durability of bamboo. Durability is affected by the seasons. During the dry seasons, susceptibility to attack by fungi is greater because of the increased starch content. Thus, the right time to harvest is during or after the rainy season. The culms should be cut such that leaves are not removed. Leaves allow for the natural evaporation of free capillary water.  

Water Leaching Methods

Submerging the bamboo culms in running or stagnant water helps the villagers to preserve the bamboo. As the culms are lighter than water, weight is put on the culms to submerge them completely in water. The fresh poles are stored for about 3 months in stagnant or flowing water. Starch, carbohydrates, and other water-soluble substances may be fermented or washed out. The duration of dipping varies from species to species. Slaked lime makes the surface of treated wood alkaline. This delays the attack of fungi. Studies have also reported that the remarkable reduction in starch content and the presence of additional amine groups in the treated samples might have contributed towards enhanced fungal resistance. Kaur et al. reported that the ability of treated samples to resist insect and microbial attack under field conditions only lasted up to six months, which was much better than the control. The water leaching method was found to be incapable of giving complete protection to the culms under field conditions.

Smoke Treatment

Smoke treatment is used in villages to enhance the durability of bamboo species. Wood stored in the kitchen over the fireplace. This process of using smoke to prevent insect attack is thousands of years old. Villagers have learned from experience that wood stored in this way are able to survive insect attack up to several years. However, no scientific data on the smoke treatment process for bamboo species can be found in the literature. It is expected that polycyclic aromatic hydrocarbons, phenols, aldehydes, ketones, organic acids, alcohols, esters, hydrocarbons, and various heterocyclic compounds present in wood smoke are able to improve the durability of wood species. If bamboo culms are fumigated (using their own branches and leaves) for a longer time, they become inedible to insects. The culms are smoked at an air temperature of 50 to 60 °C, which changes the moisture level of the air. The reduction in the water-soluble constituents including starch might help to protect the culms from fungi and insect attacks. Looking at the eco-friendly nature of the process.

 The smoke, a by product generated during the pyrolysis process for making charcoal, could potentially be a useful means to increase wood resistance to termite attack. Wood specimens were exposed to smoke for a different duration of time. The most effective duration of smoking for producing high resistance in wood is not reported in the literature.