Agronomic Factors Affecting the Potential of Sorghum as a Feedstock for Bioethanol Production in the Kanto Region, Japan

Shoko Ishikawa,Hitoshi Kato,Takayuki Tsukamoto,Kazuto Shigeta,Ken-Ichi Yakushido

doi:10.3390/su9060937

Abstract

In the Kanto region in Japan, the possibilities of running a bio-ethanol plant from rice straw has been assessed and sorghum production has been considered as a necessary part of the system. Two field experiments were conducted in 2012 and 2013 at the NARO—Agricultural Research Center in Tsukuba, Ibaraki to estimate yielding ability of sorghum in the Kanto region. Two cultivars of sweet sorghum and one of grain sorghum were sown using a pneumatic seeder. Above-ground dry matter (DM) yield ranged from 1.03 to 1.82 kg m−2 for the sorgo type cultivars and from 0.70 to 1.18 kg m−2 for the grain type cultivar. The observed yields were lower than the simulated potential yields, i.e., 1.61 to 2.66 kg m−2, indicating that biomass production was restricted in this study. Stem brix values for the sweet sorghum cultivars were generally low (3.3–16.2%) compared with the values reported in the literature. It appears that there is still room to improve the field management of sorghum to minimize the gap between the potential and actual production observed in these experiments.

Highlights

Unlike the southwest islands where sugarcane is almost exclusively expected to play a key role as a feedstock for bio-ethanol plants [1], rice straw is likely to be a major feedstock in the Kanto region [2,3]
An ethanol plant in the Kanto region with the major feedstocks being rice straw, vinasse could be applied to paddies but only at a particular time of year when rice needs nutrients for growth, while vinasse is generated in the ethanol plants all year round or close to it
To cultivate sorghum in the Kanto region especially within a global warming context, more cultivars, for example, preferably with early vigor and equipped with resistance to aphids need to be developed. Sorghum seeds of both sweet sorghum (SIL05 and FS501) and grain sorghum (8080) cultivars were sown under two field experiments conducted in 2012 and 2013 to estimate yielding ability of this crop in the Kanto region in the context of bioethanol production

Summary

Introduction

Unlike the southwest islands where sugarcane is almost exclusively expected to play a key role as a feedstock for bio-ethanol plants [1], rice straw is likely to be a major feedstock in the Kanto region [2,3]. Being stripped of energy in the form of ethanol, vinasse still contains organic matter and has a high chemical oxidative demand (COD) Releasing it casually, for example, into surface waters would be damaging to the environment and be regarded as a waste of valuable energy and nutrients. An ethanol plant in the Kanto region with the major feedstocks being rice straw, vinasse could be applied to paddies but only at a particular time of year when rice needs nutrients for growth, while vinasse is generated in the ethanol plants all year round or close to it. It would be necessary to develop cropping systems, apart from paddies, that could receive vinasse at various timings throughout the year It would be preferable if the constituent crops could contribute to the operation of the ethanol plant as feedstocks when necessary. It is known that sugarcane mills in Brazil have been altering the ratio of production of ethanol to sugar according to the demand [10], this flexibility within the biofuel industry is clearly advantageous where competition for fertile cropland for food production is concerned [11]

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