Waste green coconut shells: Diagnosis of the disposal and applications for use in other products

Highlights

• 1.7 M units of green coconut shells are wasted annually in the analyzed regions.

• The region can produce 34 M units of biodegradable tubes annually with the shells.

• Potential applications include gardening, crafts, and briquettes.

• The annual use of the shells would reduce emissions between 10.2 t and 20.9 t CH₄.

Abstract

Information about the quantities of green coconut shells disposed of in areas where the coconuts are consumed is not precise, which can make it difficult to arrange the management of these residues. Assessing the amount of coconut husk disposed of in a region, and the potential of this material for producing other products, will not only improve the environment, but will also contribute to the economic development and health of the population. Based on a structured face-to-face survey in a representative sample of seven municipalities in the southern coastal region of Bahia, this study identifies and maps the main points of consumption where the disposal of green coconut shells occurs, with an evaluation of the uncertainty of the data. The results show that the region annually wastes the equivalent of 1.7 M shell units with a standard uncertainty (u) of 1.2 k, and the amount of fibers that could be extracted for the manufacture of products is 632 t (u = 59 t). The use of the green coconut shells wasted in this region to create other products would lead to an annual reduction in emissions of between 10.2 t and 20.9 t of CH₄. A survey conducted over the past ten years of the general framework for possible uses of the shells, and an analysis of strengths, weaknesses, opportunities and threats (SWOT), have shown that green coconut shells have potential for use in the production of gardening products, handicrafts, and briquettes. Valuation based on gardening products reveals that the region could produce 34 M (u = 47 k) units of biodegradable tubes for planting seedlings annually and could therefore generate a gross annual revenue of R$ 170 000 (u = 2 350). With regards to briquettes, considering only the municipality of Ilhéus, production could generate a gross value between R$ 2 190 and R$ 3 650 per month.

Introduction

Increased consumption of coconut water and green coconut fruit pulp has increased the generation of coconut shells (Ayrilmis et al., 2011), which in some regions tends to become waste, generating negative social, economic and environmental impacts (Biggs et al., 2015). Due to the lack of management and investment by the public or private sector, these shells are not used as a raw material for production in Brazil (Santana et al., 2014).

Coconut shell accounts for around 85% of the weight of the fruit (Ayrilmis et al., 2011) and has an assumed composition of 33.30% lignin, 30.58% cellulose, 26.70% hemicellulose, 8.86% water and 0.56% ash (Arena et al., 2016). Research has shown that there is potential for the use of coconut shells, in the form of fiber or powder, for the production of semi-crystalline magnetite nanoparticles (Sebastian et al., 2018); biosorbents for Ag ion sorption (Staron et al., 2017); thermal insulation (Araújo et al., 2015); agglomerates (Fiorelli et al., 2012); panels (Ayrilmis et al., 2011); substrates for planting vegetables and fruits such as eggplants (Moreira et al., 2010), melons (Dias et al., 2011) and tomatoes (Ramos et al., 2008); blankets for soil protection (Babu and Vasudevan, 2008); paper (Senhoras, 2004); organic filters (Igwe et al., 2008; Monaco et al., 2009); as a reinforcement in polymer matrices (Das and Biswas, 2016); and in the aggregation of cement composites (Asasutjarit et al., 2007), grout (Silva et al., 2015), or concrete (Ali et al., 2012) for civil construction.

Although there are so many applications for the use of coconut shell, its manufacturing potential is not appreciated in many countries (Araújo et al., 2015). Brazil ranks fourth in the world for coconut production, and the state of Bahia leads with an annual production of approximately 550 000 t of fruit (Ibge, 2015).

It is estimated that 1.5 kg of shell is lost from each coconut consumed in the country, which indicates a quantity of up to three million tons of unused green coconut per year (Brasil, 2017). However, the amount of green coconut shells that are thrown away at the place of consumption is unknown, which makes it difficult to manage the amount of residue produced in the region (Santos et al., 2019).

The disposal of green coconut is not quantifiable, and generally occurs in inappropriate environments such as beaches and vacant lots (Corradini et al., 2009), and it is therefore associated with the pollution of public spaces, as coconut shells can take up to ten years to degrade in the environment, causing unsightliness in the urban environment, as well as becoming foci for mosquito breeding and disease transmission (Banerjee et al., 2013).

According to Salamai et al. (2019) and Moritz et al. (2016), the evaluation of the uncertainty of the quantitative diagnosis of waste green coconut shells in a region and the study of the possibilities of utilization, provides accurate information for risk management of a new production chain.

The objective of this article is therefore to identify and map the main points of consumption where green coconut shell disposal takes place along the South Coast of Bahia, in order to generate subsidies to be used in organizing the utilization of this material, characterizing wastage zones, evaluating uncertainties in the collected data, and synthesizing the potential applications of coconut shells, using the ‘strengths, weaknesses, opportunities and threats’ (SWOT) analysis tool. In addition, the valuation perspectives that have been developed over the last 10 years will be analyzed, in order to contribute to understanding the generation of economic and environmental value from products that could be manufactured in the regions where such waste occurs.