Identification and thermochemical analysis of high-lignin feedstocks for biofuel and biochemical production

Venugopal Mendu,Seth Debolt,Jungho Jae,Jozsef Stork,Andrew Placido,Samuel Morton,Mark Crocker,George Huber,Anne E Harman-Ware

doi:10.1186/1754-6834-4-43

Abstract

BackgroundLignin is a highly abundant biopolymer synthesized by plants as a complex component of plant secondary cell walls. Efforts to utilize lignin-based bioproducts are needed.ResultsHerein we identify and characterize the composition and pyrolytic deconstruction characteristics of high-lignin feedstocks. Feedstocks displaying the highest levels of lignin were identified as drupe endocarp biomass arising as agricultural waste from horticultural crops. By performing pyrolysis coupled to gas chromatography-mass spectrometry, we characterized lignin-derived deconstruction products from endocarp biomass and compared these with switchgrass. By comparing individual pyrolytic products, we document higher amounts of acetic acid, 1-hydroxy-2-propanone, acetone and furfural in switchgrass compared to endocarp tissue, which is consistent with high holocellulose relative to lignin. By contrast, greater yields of lignin-based pyrolytic products such as phenol, 2-methoxyphenol, 2-methylphenol, 2-methoxy-4-methylphenol and 4-ethyl-2-methoxyphenol arising from drupe endocarp tissue are documented.ConclusionsDifferences in product yield, thermal decomposition rates and molecular species distribution among the feedstocks illustrate the potential of high-lignin endocarp feedstocks to generate valuable chemicals by thermochemical deconstruction.

Highlights

Lignin is a highly abundant biopolymer synthesized by plants as a complex component of plant secondary cell walls
We wanted to capture the breadth of lignification across a diversity of plant families, which resulted in the inclusion of Arabidopsis as an annual Brassica (Cruciferae), despite its not being a bioenergy crop candidate
We examined the aerial portion of switchgrass (Panicum virgatum) or Poplar stem (Populus deltoides and P. trichocarpa) and included Nicotiana benthamiana stem and a range of fruit endocarp waste derived from horticultural crops grown abundantly worldwide, including olive (Olea europaea), black walnut (Juglans nigra), coconut (Cocos nucifera) and peach (Prunus persica) as characteristic species for the stonefruits [16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37] (Table 1)

Summary

Introduction

Lignin is a highly abundant biopolymer synthesized by plants as a complex component of plant secondary cell walls. The focus within the biofuels community has begun to shift from alcohol production to the production of hydrocarbon biofuels by thermochemical deconstruction. Such fuels are replacements for gasoline, diesel and jet fuel, and, given that they can function as drop-in fuels, they are far more attractive than ethanol for existing internal combustion engines [14]. The oxygenates resulting from the oxidative deconstruction of lignin can be either deoxygenated to produce hydrocarbons (for example, by (1) hydrodeoxygenation or hydrolysis and (2) fast pyrolysis [4]) or first subjected to separation to recover high-value chemicals that are present, such as phenols and cresols. Preliminary experiments were performed to examine the pyrolytic characteristics of the various feedstocks and to estimate the potential of these feedstocks to produce bioelectricity, biofuel and high-value chemicals

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Conclusion