Are natural fiber composites environmentally superior to glass fiber reinforced composites?

https://doi.org/10.1016/j.compositesa.2003.09.016Get rights and content

Abstract

Natural fibers are emerging as low cost, lightweight and apparently environmentally superior alternatives to glass fibers in composites. We review select comparative life cycle assessment studies of natural fiber and glass fiber composites, and identify key drivers of their relative environmental performance. Natural fiber composites are likely to be environmentally superior to glass fiber composites in most cases for the following reasons: (1) natural fiber production has lower environmental impacts compared to glass fiber production; (2) natural fiber composites have higher fiber content for equivalent performance, reducing more polluting base polymer content; (3) the light-weight natural fiber composites improve fuel efficiency and reduce emissions in the use phase of the component, especially in auto applications; and (4) end of life incineration of natural fibers results in recovered energy and carbon credits.

Introduction

Since the 1990s, natural fiber composites are emerging as realistic alternatives to glass-reinforced composites in many applications. Natural fiber composites such as hemp fiber-epoxy, flax fiber-polypropylene (PP), and china reed fiber-PP are particularly attractive in automotive applications because of lower cost and lower density. Glass fibers used for composites have density of ∼2.6 g/cm3 and cost between $1.30 and $2.00/kg. In comparison, flax fibers have a density of ∼1.5 g/cm3 and cost between $0.22 and $1.10/kg [1]. While, natural fibers traditionally have been used to fill and reinforce thermosets, natural fiber reinforced thermoplastics, especially polypropylene composites, have attracted greater attention due to their added advantage of recyclability [2]. Natural fiber composites are also claimed to offer environmental advantages such as reduced dependence on non-renewable energy/material sources, lower pollutant emissions, lower greenhouse gas emissions, enhanced energy recovery, and end of life biodegradability of components. Since, such superior environmental performance is an important driver of increased future use of natural fiber composites, a thorough comprehensive analysis of the relative environmental impacts of natural fiber composites and conventional composites, covering the entire life cycle, is warranted. In this article, we review select life cycle assessment (LCA) studies comparing natural fiber composites and glass fiber composites. We identify the major drivers of the relative environmental performance of natural fiber composites, and draw conclusions about whether the specific findings of these studies can be generalized.

Section snippets

Life cycle assessment

Life cycle assessment is a technique for assessing the environmental aspects and potential impacts associated with a product, by

  • compiling an inventory of relevant inputs and outputs of a product system;

  • evaluating the potential environmental impacts associated with those inputs and outputs;

  • interpreting the results of the inventory analysis and impact assessment phases in relation to the objectives of the study.

LCA studies the environmental aspects and potential impacts throughout a product's

Review of prior studies

A few studies have looked at comparative life cycle assessment of specific components made from glass fiber reinforced (GFR) composite materials and natural fiber reinforced (NFR) composite materials [4], [5], [6], [7]. We summarize the methodology and findings from three studies available in English below.

Drivers of superior environmental performance

These three studies show that in their specific applications, NFR composites are environmentally superior to GFR composites on most performance metrics. However, there are significant differences across these studies, in terms of the specific component/application being studied, material composition of the reference component as well as the NFR component, specific natural fiber chosen, production processes, boundaries and scope of the life cycle assessment, environmental impacts considered, and

Conclusions

Extant studies comparing life cycle environmental performance of natural fiber composites with glass fiber reinforced composites find that natural fiber composites are environmentally superior in the specific applications studied. We propose that NFR composites are likely to be environmentally superior to GFR composites in most applications also for the following reasons: (1) natural fiber production results in lower environmental impacts compared to glass fiber production; (2) NFR composites

Acknowledgements

Financial support for this research was provided by the National Science Foundation research grant NSF-PREMISE-225925 of 2002.

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