Pre-Feasibility Study for Coupling Electronic Waste Recycling With Desert Greening in Africa

Africa suffers from the following serious problems: (i) the distribution of desertification vulnerability suggests that every country is prone to environmental desertification, and desertification processes currently affect about 46% of the total land area; (ii) the Basel Convention is an international agreement that regulates cross-border shipments of toxic waste, but this tight regulation for prohibiting export of end-of-life electronic devices (so-called e-waste) to the third world has resulted in an increase in illegal transport to Africa. The present research is intended to conduct a technical pre-feasibility study in order to tackle the above-mentioned problems. About 80% of e-waste comes from television sets and computers, and cathode ray tubes (CRTs) correspond to about 2/3 of the total weight ‒ the neck and funnel parts of CRTs contain toxic materials. The manufacture of foam glasses is considered as safe CRT treatment. The control of soil water is significant to cultivate plants the desert, and the waste-based foam particles can improve water retention in arid soils; i.e. a key proposal is the production of soil amendment from CRT glass. The water-use efficiencies of this amendment’s layer are higher than those of the control. Furthermore, leaching fractions of heavy metals from the produced foam glass amendment are lower than the statutory limits.


Introduction
Africa is endowed with enough land to undertake actions to improve household quality, country progress, domestic and international trade, etc.There are, however, some threats and challenges (UNEP, 2008): desertification is considered as a serious problem -about one billion habitants suffer from this desertification, and the situation is growing worse in Sub-Saharan Africa (SSA) in particular.
The word "e-waste" is roughly used to electronic apparatus which is almost or at the end of its life.A global amount of this waste is annually estimated at about 50 million tons (Widmer et al., 2005).The Basel Action Network (2005) reports that the e-waste amount has been growing considerably in developed nations in particular, and some African countries have become dumping grounds for the world's e-waste -e.g. the UNEP (2009) estimates that the South African e-waste amount of end-of-life computers will increase by at least 200 % from 2007 levels in the near future.If action is not taken to appropriately treat materials, such nations have vast amounts of dangerous e-waste with severe environmental problems (UNEP, 2009).
Conducting a pre-feasibility study is one of the key activities within the project initiation phase.As the present paper intends to logically combine two solutions (desertification and e-waste in Africa), it mainly aims to justify this combination in terms of technical feasibility.Basic information about desertification and e-waste is reviewed first, followed by a description of the principal discussion.

Desertification
Based on data published by Reich et al. (2001), desertification means that soil in arid, semi-arid, and dry sub-humid lands is degraded by some aspects such as climatic change and anthropogenic causes.A desertification phenomenon damages about 46% in African land.

Drivers of Land Degradation
Land degradation reduces or destroys soil productivity, vegetation, arable and grazing land, as well as forest.In the most extreme cases, hunger and poverty set in and become both the cause and consequence of further degradation (UNCCD, 2011).Drivers of land degradation can be classified as (review in Mainguest, 2001): (i) natural, which means climatic change, reduction in rainfall, and increase in the frequency of drought, but also excessive rainfalls with destructive floods; and (ii) anthropogenic, which includes socioeconomic aspects with unavoidable feedback that desertify land by reducing its productive potential, leading to much more demand and further destruction of land.
High, sustained temperatures lasting for months with infrequent and irregular rainfall lead to drought and difficult growing conditions for plants and trees.As a result, severe hydrological imbalances jeopardize natural production systems (UNCCD, 2011).In countries where major economic resources are dependent on agricultural activities, there are few alternative sources of income, or none at all.Soil is damaged by excessive use when farmers neglect or shorten fallow periods, which are necessary to allow the soil to recover sufficiently to produce enough food to feed the population.

Countering Desertification
The desertification factors are associated with soil acidity, non-permeable soil layers, water logging, tendency to keep salts or some attributes (see Table 1).It is considered that the soil quality is an original land property or due to human-caused degradation in Africa (Oldeman et al., 1991).
Conventional techniques have been experimented in terms of diminishing the desert area and recover the degraded land, but the applied measures mainly deal with sand movement (cf.Sugiyama, 1984).It is now known that there are some techniques to manage and combat desertification -landscaping modification to reduce evaporation and erosion, regeneration of salty or degenerated soils, flood control, prevention of overgrazing and firewood use, etc.
Desert greening is usually related with a water utility.If enough water for irrigation is available, any desert can be basically greened.However, the water issue is put on a wide range of subjects such as impeded drainage, seasonal moisture stress, etc.In this paper, attention is mainly focused on the water-holding capacity of soils.The soils with low water-holding capacity occupy about 20% (5.3 million km 2 ) of the land area in Africa, and this rate is recognized as the inherent quality of African land (see Table 1).

Electronic Waste
The disposal amount of electronic devices, such as personal computers (PCs), mobile phones and so on is globally increasing (Widmer et al., 2005).It is reported that old-fashioned PCs increased from 20 million in 1994 to 100 million in 2004 (Widmer et al., 2005).The cumulative amount of disposal PCs corresponds to 2,873,000 tons plastics, 719,000 tons Pb, 1,364 tons Cd and 287 tons Hg (Puckett & Smith, 2002).This disposal tendency indicates that the PC business is not saturated and its life span is considerably diminishing: i.e. from 5 years in 1997 to 2 years in 2005 (Culver, 2013).

Transboundary Trade and Basel Convention
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Application of Foam Glass to Soil Amendment
Foam particles generally absorb water, and this absorption has a high capacity of water retention in (Andersen, 2013).Thus, there a possibility that the foam particles reduce the amount of water demand in irrigation.Furthermore, the foam particles discharge water to the plant roots as the surrounding soil moisture drops (cf.Hara et al., 2003).Heated to the softening temperature, this inorganic material will not be decomposed soil microbes, but it will act as a substrate for them (Ramsey & Ungerleider, 2007).Inorganic amendments such as porous material offer some benefits for improving sand-based root zones (Habeck & Christians, 2000); that is, they are less prone to compaction than organic materials and have higher cation exchange and water holding capacities without reducing non-capillary pore space (air-filled porosity).They are essentially permanent additions to the root zones, demonstrating very little break down over time (Habeck & Christians, 2000).

Field Test of Amendment Produced From Waste Glass
As stated in section 4.3, foam glass can be prepared from end-of-life glass through reaction with a reducing agent at a high temperature.The waste-based foam glass for soil amending has been commercialized -Porous α, Nextone α and so on (cf.Yamane & Takeuchi, 2009).A field test using such foam glass is presented according to published data (Ahmed & Inoue, 2009).The tested soil contains 95 wt% sand, 1.2 wt% silt and 3.8 wt% clay.This soil shows water holding capacity of 0.06 cm 3 cm -3 , wilting point of 0.028 cm 3 cm -3 and field capacity of 0.09 cm 3 cm -3 .The characteristics of the materials applied in this field test can be seen from Table 2. Exchangeable Na + , cmol kg -1 Cation exchange capacity, cmol kg -1 Bulk density, g cm -3 Hydraulic conductivity, cm s -1 0.012 The test field consists of two amendment layers of 2 cm and 5 cm thickness in the soil and one control without amendment.Swiss chard was sown in this field in April, and a compound NPK fertilizer 8-8-8 was applied each 10 days.A drip system was used to irrigate this filed: 40 cm of emitter distance and 2 ℓ h -1 of discharge rate with 0.1 MPa.Water irrigation started 14 days after seeding, and it continued until the harvest time in July.
The term of water use efficiency means a level of fresh yield per unit of water used up in the crop growth, and this efficiency is often considered an important determinant of yield under stress and even as a component of crop resistance (Stiles & Cocking, 1969).The efficiencies obtained from the field test are summarized in Table 3.  (Nakamoto & Yamamoto, 2010): a sample of CRT glass containing 19.1 wt% PbO was mixed with CaO as the auxiliary agent, and this mixture was melted and reduced to Pb in an iron crucible at 1,350 °C.The PbO content of 0.4 wt% was measured in the glass phase; to put it differently, the PbO contained in CRT glass can be recovered as metallic lead at a high efficiency.However, this recovery should be more technically sophisticated, and a pilot-scale test is also required to assess its feasibility and cost performance on an industrial scale.

Conclusions
Although the Basel Convention regulates cross-border shipments of toxic waste (cf.section 3.1), it is reported that embargoing e-waste trade to third nations is an idealistic attempt resulting in illegal transport (review in Mueller et al., 2012).In any case, it is important to obey this convention protecting human health and the environment from toxic waste.One problem remains in how to solve the vast amount of e-waste already exported and accumulated.The other problem is the desertification that currently affects African land in particular (section 2).The study presented in this paper aimed at discussing the combination of e-waste management with desert greening in Africa, and this combination is concluded to be feasible.

Table 1 .
Typical land stresses and inherent land quality in Africa(after Reich et al., 2001).