Biodegradable Agricultural Mulch Films from Wastepaper Pulp and Calcium Alginate

The survival of 8 billion people on the planet depends on agriculture, the cultivation of crops and the raising of livestock. In agricultural crop production, rather than organic mulches, plastic mulch films, usually made of low-density polyethylene (LDPE), are the most popular choice, because of their superior weed and pest prevention as well as their longevity. However, traditional plastic mulch films depend on non-renewable resources and are nonbiodegradable, accelerating plastic pollution with deadly environmental ramifications. Existing biodegradable mulch films are too expensive to be used commercially; this research proposes a more economically viable biodegradable mulch film consisting of wastepaper pulp, sodium alginate, and calcium chloride. Globally, 400 million tons of paper waste are produced yearly, with nearly 30% unrecycled and sent to the landfill. Thus, this wastepaper/alginate film turns something that would otherwise be trash into a useful tool. Films with different amounts of wastepaper pulp, sodium alginate, and calcium chloride were synthesized to determine an optimal combination. Wastepaper/alginate films without calcium chloride had little water resistivity and only had a lifespan of only a few days. Calcium ion crosslinking was found to significantly increase the water resistance and mechanical strength of the films. In addition, the field test proved that the films effectively prevented weeds and reduced required irrigation by half. It is concluded that these wastepaper/alginate mulch films have satisfactory performance and are cheap enough to replace LDPE films in agricultural applications, and a sodium alginate to wastepaper pulp weight ratio of between 1:9 and 2:8 is recommended.