Industrial Crops and Products 11 2000 129 – 137
Integrated utilisation of green biomass in the green biorefinery
Margrethe Andersen , Pauli Kiel
Centre for Agro-Industrial Biotechnology, Uni6ersity of Southern Denmark, Esbjerg, Industri6ej
11
,
6870
Ølgod, Denmark Accepted 8 October 1999
Abstract
Grass, clover and alfalfa are used for production of fodder pellets. In the green crop drying factories in the northern countries the drying is combined with pressing of the green crops resulting in production of large volumes
of plant juices, green and brown juice. In order to get rid of these enormous amounts of plant juice, representing an environmental threat, it is our aim to convert the simple drying industry to a whole crop utilisation factory, a green
biorefinery, where the plant juice can be used as raw material in a fermentation process. As the plant juice is very unstable, it has been necessary to develop a method for both conservation and utilisation of the juice. The plant juice
is converted to a nice universal fermentation medium by lactic acid bacteria. A number of lactic acid producing strains have been tested. Among the most productive strains, Lactobacillus paracasei ssp. paracasei P4155 is found to
be the most effective in utilising fructans and citric acid. Most carbohydrates and organic acids in the juice can be converted to lactic acid by two homofermentative lactobacilli. The highest lactic acid yield and productivity is reached
when using not-heat sterilised brown or green juice as the fermentation medium. The amount of free amino acids in the juice is increased and the content of vitamins and other important growth factors kept unspoiled by the lactic acid
fermentation. The fermented juice can be stored as it is or evaporated to a concentrated form and used in fermentation industries for production of amino acids, organic acids, enzymes etc. © 2000 Elsevier Science B.V. All
rights reserved.
Keywords
:
Lactic acid; Plant juice; Fermentation; Whole crop utilisation; Biorefinery www.elsevier.comlocateindcrop
1. Introduction
The green crop drying industry uses grass, clover and alfalfa as raw materials for production
of green pellets and solves their energy-economi- cal problems by pressing the green crop prior to
drying. The produced side stream, green or brown
juice, has until now been spread on the fields as fertiliser. Problems with pollution of the ground
water with nitrate, especially in the late autumn have, however, led to stringent regulations for the
use of plant juice as fertiliser in many countries.
Corresponding author. Tel.: + 45-752-46533; fax: + 45- 752-46540.
E-mail addresses
:
maasdu.dk M.
Andersen, p.kagro.sdu.dk P. Kiel
0926-669000 - see front matter © 2000 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 6 - 6 6 9 0 9 9 0 0 0 5 5 - 2
In Denmark, from year 1999, plant juice will only be allowed spread on green fields in the autumn
and not in the period between October 1st and February 1st.
The technology used at the green crop drying factories is in fact a first stage biorefinery with wet
separation of green crops for multipurpose use as described by Carlsson 1998.
The green pellet factories can very well be transformed to green biorefineries Kiel, 1998,
where the juice may be used for production of proteins, many different phyto-chemicals and fer-
mentation products.
Until today this has however not happened. The problem with the plant juice can be solved
by storing the juice in large lagoons from October 1st or by using the juice for other purposes. As
storage can easily result in bad smelling waste
Table 1 Chemical composition in g kg
− 1
of dry matter in green juice from first cut of different crops, and in one sample of brown juice from Dangrønt Products AS Ringkøbing, Denmark
a
Green juice from Chemical composition of
Brown juice Green juice from
Green juice from dry matter g kg
− 1
Italian rye-grass 27–98 clover grass 275–98
96–98 alfalfa 106–98
462.1 9 1.3 449.4 9 3.6
Water soluble carbohydrates, 330.8 9 1.9
137.0 9 1.3
b
WSC 135.8 9 1.0
219.5 9 2.7 283.1 9 1.9
355.0 9 8.8 Free carbohydrates
107.1 9 10.1 166.3 9 5.5
111.3 9 4.6 ‘Fructan’
3.2 9 0.1 5.7 9 0.2
15.2 9 0.4 5.6 9 0.01
Succinic acid 53.5 9 0.8
5.7 9 0.2 Malonic acid
17.7 9 0.2 6.5 9 0.2
16.3 9 0.1 8.9 9 0.1
14.6 9 0.2 Citric acid
8.3 9 0.1 33.7 9 0.8
36.9 9 0.9 Malic acid
42.8 9 1.0 24.3 9 0.01
5.0 9 0.1 Acetic acid
Lactic acid 3.3 9 0.1
63.1 9 1.0 Formic acid
4.5 9 0.2 98.7 9 1.8
120.8 9 1.4 Total organic acids
92.4 9 2.0 62.9 9 1.5
174.0 9 1.2 215.0 9 16.7
264.2 9 15.3 Protein N×6.25
349.0 9 6.8 Dry matter
5.94 9 0.01 3.38 9 0.01
6.02 9 0.005 5.38 9 0.001
a
All samples were taken in MayJuneJuly 1998.
b
Determinations in triplicate.
Fig. 1. Seasonal variations in content of free and fructan bound sugars, organic acids and dry matter in brown juice.
Fig. 2. a Growth curve and base-titration curve for a batch fermentation of MRS broth by L. sali6arius BC 1001. b
Growth curve and base-titration curve for a batch fermenta- tion of brown juice by L. sali6arius BC 1001. The brown juice
was added glucose to reach the same sugar concentration as in the MRS broth.
Lier, 1994; Mu¨ller and Steller, 1995. The aim of this study is to find a way of simultaneous preser-
vation and utilisation of plant juice for fermenta- tion purposes.
2. Materials and methods
