**1. Introduction**

Cocoa (*Theobroma cacao* L.) is one of the most cultivated and valuable crops in many developing tropical countries including Ivory Coast, Ghana, Nigeria, and Cameroon whose collective efforts alone accounts for about 74.5% of annual global cocoa beans. Three species of *T. cacao* L. (*Sterculiaceae*) namely *Criollo*, *Forastero*, and *Trinitario* are the dominant market produce and commercial cocoa species of all 22 species present in that genus [1].

Cocoa pod husks (CPH) are the non-edible part of the cocoa pod with a percentage composition of 67–76% of the total cocoa pod wet weight. This translates to every kilogram of dry cocoa bean produced generating 10 kg of wet cocoa pod husks [2]. For instance, it has been estimated that the annual world crop of 1 million tons of cocoa produces about 10 million tons of pod husks as by-product, and constitutes about 67% of the fresh pod weight. After removal of the cocoa beans, treated and exported abroad, CPH is usually discarded on the farm, which often is left to decompose as an organic fertilizer. However, CPH left on the soil surface also act as a source of inoculum for plant diseases such as black pod rot (BPR) due to the development of *Phytophthora* spp. bacteria. BPR causes an annual cocoa yield loss from 20 to 30% worldwide, while individual farms may suffer an annual cocoa yield loss from 30% up to 90%. A graph of the production of cocoa bean and cocoa pod husks generated from around the world by countries known to be among the leading producers of cocoa is shown in **Figure 1**.

The development of cutting-edge technologies that can efficiently transform these hitherto waste materials generated from cocoa into useful chemicals that could potentially improve the global value chain of cacao production, is crucial and highly sort after and concomitantly reduce the negative environmental impact. Many researchers have developed interests in this area of study because of the vast availability of CPH which poses a major waste management challenge confronting cocoa-producing nations. In light of this, there have been multiple reports on the valorization of CPH into value-added products in an attempt to contribute to our drive for a sustainable society and a circular economy. Nonetheless, CPH have been hugely underexploited even though there have been numerous published literatures on this subject matter. In fact, research interest in CPH valorization dates back 1905 with a single publication. The publications increased significantly from 2003 and has continued to grow ever since. Averagely, for the past decade there has been about 18 publications per year on CPH (**Figure 2**).

Majority of these publications related to CPH were journal articles, hugely representing over 50% of the global works related to CPH transformations to various value-added products. However, a number of patents have also been filed (representing about 15% of the global publications related to CPH transformations),

**Figure 1.** *Generation of cocoa bean and cocoa pod husks by various countries.*

*Conventional and Unconventional Transformation of Cocoa Pod Husks into Value-Added… DOI: http://dx.doi.org/10.5772/intechopen.102606*

**Figure 2.** *Publications produced annually related to CPH transformations.*

**Figure 3.** *Publication work density on cocoa pod husks (reproduced and modified with permission from: Ref. [3]).*

signifying the importance of the works and results discovered in relation to CPH as a bio-resource raw material. **Figure 3** below shows the work density by type of publication CPH.

The renewed and increased interest in CPH can be attributed to the enormous quantities generated on the farm, the environmental challenge that rotten CPH poses as well as the concomitant spread of black pod diseases that has accounted for the huge losses recorded by cocoa farmers [1–3]. Besides CPH has been found to be a valuable bio-resource due to the myriad of value-added products such as activated carbon, soap, animal feed, soil manure and fertilizer, biofuels, paper, biofuels, and

nutraceuticals that it can be transformed into. It has also been found to be a repository of base chemicals of high value such as aldehydes, ketones, theobromine, phenols, potash, and pectin [4–9]. CPH applications in several areas including radial electrochemical agrochemical bio-regulators, thermal energy technology, soil fertilization, manure and fertilizer production, food and animal chemistry, plastic treatment and waste treatment, and disposal are still being explored. Whilst soil fertilization, plant nutrition, and food and feed chemistry aspects of CPH application have been extensively exploited, plastic manufacturing, and processing is still underexplored and deserve special attention [3]. Compositionally, CPH comprises of mesocarp, sclerotic part, and epicarp (**Figure 4**).

Primarily, CPH consists of fibrous materials that includes ~19–26% cellulose, 9–13% hemicellulose, 14–28% lignin, and 6–13% pectin. The mesocarp contains mainly (~50%) cellulose, while the epicarp is enriched with lignin and the endocarp on the other hand rich in pectic substances [9]. The hemicellulose fraction of CPH has been reported to consist of arabinan, arabinoxylan, and xylan, which have been deduced from the high amount of isolable arabinose and xylose [10], along with other hemicelluloses fractions such as xyloglucans, galactomannans, and

**Figure 4.** *Fresh cocoa pod fruit (a) and dried cocoa pod husk (b and c).*

*Conventional and Unconventional Transformation of Cocoa Pod Husks into Value-Added… DOI: http://dx.doi.org/10.5772/intechopen.102606*

glucomannans [11]. CPH is also a good source of phenolic acids, with quantities ranging from 4.6 to 6.9 g GAE/100 g.

Numerous technologies and transformation routes have been explored for the valorization of CPH into valuable products. Among these transformation routes are biochemical, physical, physicochemical, and thermochemical processes. Unconventional valorization routes such as supercritical carbon dioxide extraction, microwave, and ultrasound technologies have also been investigated and are still under exploration.

The main objective of this chapter is to shed light on some of the scientific efforts tailored at valorizing CPH either by conventional or unconventional approaches into valuable platform chemicals and products, as well as the challenges and future perspectives on the efficient use of CPH as a potential agro-waste resource and its economic viabilities.
