Abstract
We have calculated that with the world population projected to increase from 7.5 billion in 2017 to 9.8 in 2050, the next generation (within 33 years) will produce 12,000–13,000 Mt of plastic, and that the yearly consumption will reach 37–40 kilos of plastic per person worldwide. One of the branches of the plastics industry is the production of plastics for agriculture e.g., seed trays and pots. In this paper, novel metakaolin-based geopolymer composites reinforced with cellulosic fibres are presented as an alternative to plastic pots. Materials can be dedicated to agricultural applications, provided they have neutral properties, however, geopolymer paste and its final products have high pH. Therefore, a two-step protocol of neutralisation of the geopolymer foam pots was optimised and implemented. The strength of the geopolymer samples was lower when foams were neutralised. The reinforcement of geopolymers with cellulose clearly prevented the reduction of mechanical properties after neutralisation, which was correlated with the lower volume of pores in the foam and with the cellulose chemical properties. Both, neutralisation and reinforcement with cellulose can also eliminate an efflorescence. Significantly increased plant growth was found in geopolymer pots in comparison to plastic pots. The cellulose in geopolymers resulted in better adsorption and slower desorption of minerals during fertilisation. This effect could also be associated with a lower number of large pores in the presence of cellulose fibres in pots, and thus more stable pore filling and better protection of internal surface interactions.
Highlights
The exponential increase of the world’s population and production intensity causes a lot of environmental problems, amongst them, an unparalleled volume of generated waste [1,2]
Low-cost geopolymer foam materials could be produced from metakaolin and sand, using an alkali activation process (NaOH) and foaming agents (H2 O2 )
The excellent potential of a two-stage neutralisation method was demonstrated, which allows the use of geopolymers for the production of pots with approximately pH 7, and for plant cultivation
Summary
The exponential increase of the world’s population and production intensity causes a lot of environmental problems, amongst them, an unparalleled volume of generated waste [1,2]. The pollution of natural ecosystems with waste plastics is one of the most massive and urgent problems. It is estimated that the current global production of plastic reaches 350–380 Mt with a compound annual growth rate of 8.4% [3]. The total economic damage to the world’s ecosystems caused by plastic, amounts to at least. The generation will produce 12,000–13,000 Mt of plastic, and the yearly consumption will reach 37–40 kilos of plastic per world citizen. In order to limit the harmful effects of plastic production on the environment, and in turn human health, appropriate waste management is necessary. On 24 October 2018, members of the European Parliament voted
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