Contents lists available at ScienceDirect Industrial Crops & Products journal homepage: www.elsevier.com/locate/indcrop An extractor for unloading the wet biomass stored in silo-bag Alberto Assirelli ⁎ , Enrico Santangelo Consiglio per la ricerca in agricoltura e l’analisi dell’economia agraria (CREA) – Centro di ricerca Ingegneria e Trasformazioni agroalimentari, Monterotondo, Rome, Italy ARTICLE INFO Keywords: Storage Unloading machine Corn silage Biomass Bioenergy Biogas ABSTRACT The storage of wet biomass can produce some problems when the biomass is emptied from silo-bags. Its extreme compactness and adhesion to the extractor cause clogging and product loss. Despite the importance of such an operation, the problem of silo-bag emptying has been addressed only rarely. This paper describes a new pro- totype of extractor designed for unloading the wet biomass from silo-bags. The machine was tested on silo-bags (of a capacity of around 200 t) filled with corn silage stored for two months. The study analyzed the qualitative parameters of the feedstock (density, moisture content, and particle size distribution), and the performance of the extractor in working conditions at three forward speeds (14.4, 18.0, and 21.6 m h -1 ). The extraction ca- pacity of the machine proved comparable at the three speeds, but the maximum value (38.5 kg cm -1 ) was achieved at 18.0 m h -1 . This speed, however, resulted in some clogging problems which caused a reduction in the working time (23.5%). Overall, the productivity proved satisfactory, ranging from 50.5 (at a forward speed of 14.4 m h -1 ) to 82.6 t h -1 (at a forward speed of 21.6 m h -1 ), while the material losses caused by the me- chanical action of the extractor were low (0.09% w/w). 1. Introduction The use of silo-bags to store dry grains and wet biomass to be used for food, animal feed, and bioenergy production was first introduced in the early 1990s in Argentina, later spreading to more than 40 countries worldwide (Barreto et al., 2013; Darby and Caddick, 2007). Argentina is currently the world leader in this technology (Casini et al., 2009), but a widespread use of silo-bags has also been reported in the USA (Muck and Holmes, 2006; Subramanyam et al., 2012), Canada (Jayas et al., 2011), and Australia (Darby and Caddick, 2007), while in other coun- tries such as Italy the system is in the initial study stage (Pezzuolo et al., 2016). Silo-bag storage can be considered an on-farm “buffer” man- agement option (Darby and Caddick, 2007) with some advantages. The hermetic sealing ensured by the plastic bag protects the biomass from water, while the airtightness of silo-bags makes it possible for the CO 2 produced by the respiration of biotic components (correspondingly consuming O 2 ) to be kept inside, thus contributing to controlling the insect population (Barreto et al., 2013; Busato et al., 2011; Chelladurai et al., 2016; Darby and Caddick, 2007). The silobag proved to be easy to manage because it does not require fixed cost structures and can be a prompt solution for temporary surplus, while at the same time in- creasing the harvest window of high-moisture biomass (Darby and Caddick, 2007). This technique has mainly been applied to grain silage and has been used for corn, wheat, barley, canola, soybean, and sunflower (Bartosik, 2012; Ochandio et al., 2010), but its use can be extended to energy crops (Corno et al., 2016). To some extent, the idea of using it for en- ergy crops has given new impetus to the sector and led to new ideas for additional improvements. Over the past ten years, in fact, the growing demand for vegetable oils as a renewable energy source (biodiesel) has increased the import of soybean, canola, sunflower, and palm into the European Union (Ochandio et al., 2010). The estimation of the biomass required for energy use in 2020 is 136 million tons (Lewandowski, 2016), leading to a growing demand for more storage capacity. Such a trend requires the set-up of storage solutions which are economically sustainable, efficient, and able to ensure the quality of silage and lower dry matter losses. In Italy, the increased biogas production has been fast enough in recent years to make it the second European country in number of plants (Carrosio, 2013), most of which are mainly fed with corn and other grain silage stored wet (Dinuccio et al., 2010). As shown by Pezzuolo et al. (2016), the storage of corn for anaerobic digestion could benefit from the adoption of the silo-bag system, which makes it pos- sible to reduce costs by 7% and energy use by 8%. The environmental impact of corn ensilage proved to be lower (from –5% to –9%) when the silo-bag was used instead of the bunker silo, a difference mainly due to a lower loss of dry matter (Bacenetti and Fusi, 2015). New insights are becoming available concerning the ensilage of other interesting energy crops which are suitable for anaerobic digestion, such as giant reed (Arundo donax L.) (Liu et al., 2016), while other studies have https://doi.org/10.1016/j.indcrop.2018.06.051 Received 29 January 2018; Received in revised form 8 June 2018; Accepted 12 June 2018 ⁎ Corresponding author. E-mail address: alberto.assirelli@crea.gov.it (A. Assirelli). Industrial Crops & Products 123 (2018) 128–134 0926-6690/ © 2018 Elsevier B.V. All rights reserved. T