Cellulose
(b)
Fig. 7 Visually estimated degradation rates for paper sheets ( a ) andpots ( b ),when exposed to different soils
(a)
80
80
sand
forest
agricultural
sand
forest
agricultural
70
70
60
60
50
50
40
40
30
30
20
20
10
10
0
0
WP WP3W WP5W WP3R WP5R paper type
WP WP3W WP5W WP3R WP5R comercial pots pot type
Conclusions
All tested paper configurations could be suitable for manufacturing plantable bio-containers that will slowly disintegrate during their lifespan. Their use improves both the sustainability and public perception of the investigated products. However, in addition to environmental and economic aspects, the effect of alternative containers on plant growth and quality should be considered. Therefore, our future work will be related to calculation of environmental impact of manufactured paper packaging products. Proper use of the experimental results may help in selection of products with optimal composition for specific appli- cations, including pots used in horticulture or for forest nurseries. Moreover, by proper fillers selection, pack- aging products with custom degradation rate best suited to certain crop cycle durations and adopted for specific types of soils may be designed. Part of this work was conducted within the framework of the project BIO4ever (RBSI14Y7Y4) funded within the SIR (Scientific Independence of young Researchers) call by MIUR. The authors gratefully acknowledge the European Commission for funding the InnoRenew CoE project (Grant Agreement #739574) under the Horizon2020 Widespread-Teaming program and the Republic of Slovenia (Investment funding of the Republic of Slovenia and the European Union of the European Regional Development Fund). Acknowledgments Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http:// creativecommons.org/licenses/by/4.0/), which permits unre- stricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Com- mons license, and indicate if changes were made.
The cereal bran used in this experiment was charac- terized by a relatively high starch content. Starch promotes the binding of natural fibres during paper manufacturing and consequently improves the paper strength. Mechanical properties are particularly impor- tant in the production and utilization of paper pots manufactured from recycled fibres. The addition of cereal bran improved the mechanical properties of paper products tested in this study; paper pots with bran fillers were less susceptible to mechanical damage, when compare with commercial products. The biodegradation rate of pots changes with the quantity of added bran. Biodegradation in these pots is generally slower than in commercial pots containing peat, but faster than in pots without fillers. It was concluded that the extent of decomposition does not extensively depend on the type of filling (rye or wheat cereal bran), but rather on the quantity of filler added, exposure time and soil type. Depending on the soil type, water holding capacity and pH, soil may stimulate or inhibit the growth of microorganisms responsible for the decomposition of paper products. Paper samples (both sheets and pots) in all tested configurations degraded most rapidly in agricultural and forest soils, while biodegradation proceeded slowly in the sand soil. Analysis of NIR spectra revealed that the most advanced degradation occurred in agricultural soil. The organic content accelerated the degradation rate within all investigated papers. In contrast, sandy soil, which is low in organic matter, resulted in the lowest degradation rate and inhibited degradation processes.
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