Perspectives of Using Lignin as Additive to Improve the Permeability of In-Situ Soils for Barrier Materials in Landfills

Lucio Di Matteo,Antonio La Viola,Lorenzo Bulletti,Vincenzo Piscopo,Eliana Capecchi,Davide Piccinino

doi:10.3390/su12125197

Lucio Di Matteo, Antonio La Viola + Show 4 more

Open Access

https://doi.org/10.3390/su12125197

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Journal: Sustainability	Publication Date: Jun 25, 2020
Citations: 7	License type: CC BY 4.0

Affiliation: University of Perugia, Tuscia University

Abstract

Very often, in-situ soil does not meet the requirements for landfill barriers; therefore, it is necessary to purchase the material from quarries. An increasing number of by-products have been proposed as alternative landfill barrier materials. The present study investigated the performance of two soils of Central Italy (alluvial and volcanic soils) with an organosolv lignin (sulfur-free lignin (SFL)), a widespread by-product in the world. Laboratory investigations indicated that the volcanic soil mixed with 10% in weight of lignin did not reach the permeability value required for landfill bottom liners, also showing high compressibility. On the contrary, the addition of 20% to 30% lignin to the alluvial soil reached the permeability value recommended for the top-sealing layer of landfills: scanning electron microscope analysis indicated that the improvement was due mainly to the physical binding. Large-scale investigations should be carried out to evaluate the long-term performance of the mixtures. The increasing production of organosolv lignin worldwide gives this by-product the opportunity to be used as an additive for the realization of the top-sealing layer. The approach can save the consumption of raw materials (clayey soils from quarries), giving lignin a potential new field of application and recovering in-situ soils.

Highlights

The use of recycled materials for improving physico-mechanical and hydraulic properties of compacted earth structures is nowadays one of the main targets in engineering and environmental geology
Considering the hypothesis of the potential improvement of the permeability values of in-situ soils by adding the organosolv lignin, the objective of the study was to investigate the performance on two fine-grained soils widely outcropping in Central Italy, which do not meet the permeability requirements for landfill barriers
− The hydraulic conductivity of soil spoailrewditthootuhtelsigonilinw(itShBo).ut lignin (SB) amended with 10% in weight of lignin did not reach the values required for landfill bottom liners (k < 10−7 cm/s)

Summary

Introduction

The use of recycled materials for improving physico-mechanical and hydraulic properties of compacted earth structures is nowadays one of the main targets in engineering and environmental geology. The adding of organosolv lignin to in-situ soils may improve the hydraulic properties of compacted materials, making them potentially useful in the realization of landfill bottom liners and capping systems. This hypothesis needs to be verified, investigating-at laboratory scale the effect of lignin on some soil types. For a lignin content of about 28%–30%, the soil met the minimum permeability requirements for compacted top-sealing layers (k < 10−6 cm/s) For this mixture, the FSR was about 1.9: according to FSR classification [47], this value falls in the swelling class materials with (P200) increased to about 60%, affecting k-values. A similar mechanism has been recently proposed by reference [30], indicating that the stabilization mechanism differs from traditional soil stabilizers (i.e., lime)

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