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 to external threats including pests and disease and weather events, and a reduced capacity to provide ecosystem services such as erosion control and nutrient recycling. Thus they may also lead to a lower productivity in the long run. Intensive management which includes the use of inorganic fertilizers and pesticides acts to simplify the structure of the forest ecology, decreasing species richness and biological diversity of the tree, shrub, and herb layers, and decreasing soil microbial activity and diversity. A loss of biodiversity in bamboo forests is a potential threat to long term sustainability and also reduces the ability of bamboo forests to provide important non-timber functions such as erosion control, water catchment regulation and carbon sequestration. Nayak & Mishra (2016) have shown that increasing the density of bamboo culms per unit of land effectively creates monoculture forests with declining plant diversity, matched in turn by declines in soil fungi and bacteria diversity by up to 90%, and a lower avian diversity. Further problems arise in the case of selective logging where bamboo is used to replace trees in subtropical forests, leading to decreased overall carbon storage (Zaninovich et al, 2017). Chemical inputs present yet another concern. The highest growth rates have been recorded in drip irrigated plants where NPK and organic manure were given in combination (Aseri et al, 2012). But it has been observed that some small local bamboo processing factories have thereby caused pollution into soil and water systems (Song et al, 2011). With regard to carbon sequestration, the environmental benefits of bamboo are negated if plantations replace other felled forest types. And in regard to bamboo species diversity, some are considered invasive under certain conditions and, although bamboo typically withstands dry seasons better than many trees, the bamboo life cycle ends in a mass mortality event every few decades (Ferreira et al, 2020). These observations point to challenges in large scale plantation management since bamboo requires considerable inputs and management to be produced commercially. It has been suggested than that a smallholder model is unlikely to be able to provide enough high quality resources for a large scale industry (Rebelo & Buckingham, 2015), unless labour-intensity forms part of a social development strategy. An appropriate balance, it seems, is yet to be devised.

Conclusion / way forward Characteristics of bamboo such as its rapid growth, high biomass productivity, self-regeneration and tolerance of poor soil conditions make it a preferred alternative to a variety of materials. By implementing conservation-friendly models from an early stage, high yields can be maintained without reducing the long term viability of the forests. Viable management techniques have been identified which can ensure economic yields in the short run without compromising ecosystem biodiversity, and thus lead to long term sustainability (Yiping & Henley, 2010). Although bamboo thrives in high rainfall zones, it can also be cultivated in semi-arid areas. According to Project Drawdown (2020), bamboo can thrive and sequester carbon on otherwise inhospitable degraded lands. It is high on the list (31 of 76) of potential climate solutions. It can be utilized in a wide range of climate-friendly practices including regenerative cropping, agroforestry, forest restoration, plant-based foods and alternative building materials. Bamboo does not solve the climate crisis. But its use, and the growth of the sector, seem to offer many positive benefits when plantations and the supply chain are managed appropriately. There is always a danger that a short term profit motivation may counter-indicate longer term sustainability. But the conclusions of this review seem to confirm that “bamboo products, if based on best-practice technology, even when used in Europe, can actually be labelled ‘carbon neutral or better’” ( Van der Lugt & Voigtländer, 2015).

Limitations and obstacles This paper has identified and confirmed a range of environmental benefits conferred by bamboo and bamboo products when compared with, or substituted for, other materials and products. However, it has not considered the relative environmental impacts of product manufacturing processes, nor examined in detail optimum growing and harvesting methods and conditions. It is not therefore meaningful to state that bamboo is in all cases to be preferred without considering the full product life cycle and value chain.

In terms of the adoption of bamboo fiber in, for example textiles and paper making, previous research by this author (Shelley, 2020) has shown that supply chains tend to be dominated by well established global corporations who have shown little willingness to adopt more environmentally friendly practices. This leaves open the opportunity for newer, more ethical, organisations to forge their own position in this increasingly important market.

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The author is an environmental researcher, writer and consultant and may be contacted on [email protected]

Published by Strategic Alignment Ltd. https://strategicalignmentltd.com York, England