Bamboo and the Environment
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Bamboo and the environment Steven V Shelley MA BSc, Hope Valley, England November 2020 Introduction Bamboo is an unusual forest plant in that it’s not a tree. It’s a grass, much faster growing than trees, with a distinctive long term life cycle of mass flowering and die-off. There are reckoned to be some 1200 species worldwide (Bystriakkova et al, 2004). Bamboo has long been utilised for a wide variety of purposes including, in the modern economy, paper making, construction materials, textiles and combustible biomass, in addition to its more traditional use for furniture, as a craft material and as food (Hossain et al, 2015). With the current attention on climate change, deforestation, biodiversity loss and sustainability, bamboo has come under the spotlight for its apparent environmental advantages. This present paper reviews these claims by means of a comprehensive literature review to test the hypothesis that bamboo offers a sufficient range of economic and environmental benefits that it should be promoted more widely. The converse is also examined, that bamboo harvesting may be associated with significant environmental costs. Environmental issues The world is facing a climate crisis which can be mitigated only by reducing greenhouse gas emissions, increasing the sequestration of carbon dioxide and restoring biodiversity loss (Shelley, 2019). In practice, there are relatively few high level actions which can be taken in addition to abandoning the use of fossil fuels. One would be to slow and halt the destruction of forests while increasing the planting of carbon-absorbing plants. Another would be to replace high impact crops and products with those that are less damaging or which contribute positively to a solution. For such approaches to work at scale and at speed, there would need to be a sufficient economic incentive. The argument is that bamboo is one such crop which possesses several advantages. Although the bulk of extant literature focuses on the social and economic value of bamboo, a number of papers have drawn attention to environmental issues, including: • the potential for reforestation and a net gain in biodiversity (Rebelo & Buckingham, 2015) • increased carbon sequestration, ‘mitigating the impact of future climate change’ (Song et al, 2011) • erosion control, soil stabilization and water retention (Lu et al, 2019), and • a source of renewable energy as biomass (Scurlock et al, 2000). In support of these benefits, researchers have pointed to bamboo’s rapid rate of growth; its ability to regenerate without replanting; and to its adaptability to climate, terrain, plantation types and harvesting methods. Claims and evidence Several authors have noted that the environmental impacts of bamboo have been relatively little researched, especially in regard to numerical data on growth and sequestration, and in the form of comprehensive Life Cycle Analyses (LCA) for bamboo products (Manandhar et al, 2019). More research seems to have come out of China than other regions. China is the world’s biggest producer and exporter of bamboo and bamboo products, although as a crop bamboo is of interest in many other parts of the world including India, Africa and the Americas. A number of international agencies are devoted to researching and promoting bamboo. These include INBAR (International Bamboo and Rattan Organisation) and EcoPlanet Bamboo. These organisations focus on the commercialization of bamboo and bamboo products and have published useful papers. RATE OF GROWTH A 20m bamboo culm can replace itself within 50 days, as opposed to a 20m hardwood tree which can take decades to grow (Akwada & Akinlabi, 2016). Bamboo can be harvested 3–4 years after planting and yearly after that. Annual harvesting keeps both the clump and the forest healthy. When bamboo is harvested, the root system is unharmed and is ready to produce more shoots. Wherever bamboo is planted for reforestation and soil protection, it can be inter-planted with other crops (Manandhar et al, 2019). Its fast growth is an indication of its high capacity for carbon storage, suggesting a potentially important role in climate change mitigation (Yiping & Henley, 2010) CARBON SEQUESTRATION With their rapid growth rate and high annual regrowth after harvesting, bamboo forests have high carbon storage potential. Due to its fast growth, bamboo is widely regarded as an ideal plant to sequester carbon (Song et al, 2011). Yiping et al (2010) consider that bamboo’s sequestration ability is on a par with that of fast growing soft wood trees. This high annual rate of carbon accumulation indicates that the bamboo forest is one of the most efficient types of forest vegetation for carbon fixation (Rebelo & Buckingham, 2015), which points to the possibility of successful carbon farming if stands are managed efficiently (eg sufficient water, adequate nutrients, appropriate thinning/harvesting) (Yuen et al, 2016). Unlike trees, which are usually clear cut, the regular and selective harvesting of bamboo culms doesn’t kill the plant or damage the ecosystem, while below-ground carbon is not emitted as the bamboo forest continues to live on after harvest. There are no net carbon emissions, as carbon captured in the plant when it grows continues to be stored in the products the plant is used to produce, and is only released at the end of the product’s life when it degrades or is burned. The potential for high carbon storage potential is realized especially when the harvested culms are transformed into durable products (Song et al, 2011). The high annual yield of bamboo is not typically accounted for in LCA and carbon footprint calculations, and can therefore be considered an additional environmental advantage on top of carbon neutrality (Van der Lugt et al, 2011). Credits for carbon sequestration, and bioenergy production during the end-of-life, exceed the emissions during production and shipping, which means that many bamboo products are actually carbon negative.(Van der Lugt & Voigtländer, 2015). DEFORESTATION AND BIODIVERSITY Bamboo forests are important for biodiversity, providing food and shelter to large animals and birds, as well as soil organisms, insects, and other plants and shrubs that make up the bamboo forest ecosystems (Yiping & Henley, 2010). According to Rebelo & Buckingham (2015), bamboo could play a prominent role in forest and landscape restoration and become a major renewable and sustainable crop. Commercial bamboo plantations can help achieve forest restoration goals by using degraded and deforested land to restore critical ecosystem functions, while producing a sustainable source of fibre. RENEWABLE BIOMASS Bamboo shares a number of desirable characteristics with certain other biofuel feedstocks, including a low ash content and alkali index. Its heating value is lower than many woody biomass feedstocks but higher than most agricultural residues, grasses and straws. Bamboo has similar growth characteristics to miscanthus. Hong et al (2011) found no significant differences between bamboo and miscanthus in terms of cellulose, semi-cellulose, lignin and ash content. Although non-fuel applications of bamboo biomass may be actually more profitable than energy recovery, there is also the potential for on-site co-production of bioenergy to power the processing of bamboo (Scurlock et al, 2000). PRODUCT REPLACEMENT Not only does bamboo offer direct environmental advantages but its use can also mitigate the environmental damage cause by other crops and materials. As a source of fibre, it can replace cotton in textiles and conifers for paper pulp. As a construction material, it can replace energy intensive materials such as bricks, tiles and cement (Manandhar et al, 2019). Chen et al (2019) consider bamboo to be an important raw material for pulping and paper making in mitigation of a shortage of wood resources. Bamboo is a better raw material for pulping and paper making compared with other non-wood fibers such as rice and wheat straw, reed and bagasse, in spite of technical challenges in alkaline spent liquor recovery process and in silicon removal processing. ADAPTABILITY FOR RECLAIMING WASTELANDS Bamboo forests are excellent at controlling soil erosion in water catchment areas, and bamboo has been used successfully to rehabilitate degraded land to productive use (Yiping & Henley, 2010). With its durable root structure, which enables growth in difficult habitats such as eroded slopes, bamboo can be used to protect riverbanks, prevent landslides, and rehabilitate degraded land. Water conservation is enhanced by leaf litter accumulation, moisture retention and rainfall interception. It won’t grow equally well everywhere, however. The major factors controlling bamboo growth and distribution are temperature (the suitable mean annual temperature ranges from 15 to 20 °C), precipitation (the suitable mean annual precipitation ranges from 1000 to 2000 mm), and soil pH (suitable pH ranges from 4.5 to 7.0) (Song et al, 2011). But according to Manandhar (2019), several species of bamboo are drought-tolerant and can be cultivated in semi-arid regions where it is advisable to identify an inter-crop species that is a resident of the particular ecosystem (Aseri et al, 2012) Caveats A number of authors have observed that the environmental benefits of bamboo are not a given and that appropriate management practices are essential. Yiping & Henley (2010) state that while intensive management practices may lead to higher yields in the short run, in the long run such forest ecosystems experience a reduction in resilience