Biosystems Engineering (2004) 87 (2), 209–223 doi:10.1016/j.biosystemseng.2003.10.013 Available online at www.sciencedirect.com SE}Structures and Environment Mechanical Design Requirements for Low Tunnel Biodegradable and Conventional Films D. Briassoulis Department of Agricultural Engineering, Agricultural University of Athens, Iera Odos 75, 11855 Athens, Greece; e-mail: briassou@aua.gr (Received 6 January 2003; accepted in revised form 16 October 2003; published online 23 December 2003) The adequacy of various formulations of biodegradable agricultural films for low tunnels depends primarily on their mechanical behaviour and, of course, on their biodegradability behaviour, as compared to the corresponding behaviour of conventional low tunnel films. In the present work, the mechanical design requirements for low tunnel fully biodegradable as well as conventional films are defined. These requirements are crucial in terms of the adequacy of commercially available or new agricultural films as well as for defining the minimum allowable thickness of thin biodegradable films. Impact and tear resistance requirements and the effect of degradation are not considered in the present work. # 2003 Silsoe Research Institute. All rights reserved Published by Elsevier Ltd 1. Introduction It is the reality today that sustainability, industrial ecology, eco-efficiency, and ‘green’ chemistry are guiding the development of the next generation of materials, products, and processes (Mohanty et al., 2002). Biode- gradable plastics can form the basis for sustainable, eco- efficient products and under certain conditions, they may compete and capture markets currently dominated by products based exclusively on petroleum feedstock and thus promote independence from fossil fuel. The development of sustainable products such as biodegrad- able plastics, requires not only the consideration of production processes but also, of adequate functional behaviour for a given application, as well as concepts for the biodegradation of the post-use products. The significant interest in the use of mulching and low tunnels for protected cultivation (Chandra & Rustgi, 1998) has led to a rapid increase in the marketing of plastics used for these purposes in Europe involving hundreds of thousands of hectares and thousands of tonnes of plastic films per year (Dilara & Briassoulis, 2000). As a large portion of the plastic wastes is left on the field or burnt uncontrollably by the farmers, a practice which is not allowed any more in Europe, the use of biodegradable materials appears as a challen- gingly attractive alternative for enhancing sustainable and environmental friendly agricultural activities in mulching and low tunnel cultivation. The adequacy of various formulations of biodegrad- able agricultural films for low tunnels depends primarily on their mechanical behaviour and, of course, on their biodegradability behaviour and price, as compared to those of conventional low tunnel films. A literature review on the mechanical behaviour of biodegradable and partially biodegradable materials, with special emphasis placed on films, is presented in the work of Briassoulis (2003a). In the same work, selected critical mechanical properties of experimental, fully biodegrad- able, agricultural films (original films; before their use or degradation) are investigated and compared against those of conventional agricultural films. These experi- mental, innovative, fully biodegradable, mulching films and films for low tunnels are developed in the course of a current European project on bioplastics. At the moment there is no method or procedure available for defining or calculating the mechanical design requirements of low tunnel films. There is no relevant information in the literature available. As a result the films are designed/used based on empirical estimations. The objective of the present work is to define the mechanical design requirements for low tunnel biodegradable and conventional films. These requirements are critical in terms of the adequacy of ARTICLE IN PRESS 1537-5110/$30.00 209 # 2003 Silsoe Research Institute. All rights reserved Published by Elsevier Ltd