a quantitative assessment of crop residue feedstocks for biofuel in north and northeast china
TRANSCRIPT
A quantitative assessment of crop residue feedstocks forbiofuel in North and Northeast ChinaLU YANG* † 1 , X IAO YU WANG* † 1 , L I PU HAN* ‡ , HUUB SP I ERTZ § , SHU HUA L IAO * ,
MAO GU I WE I * † and GUANG HUI XIE*†
*College of Agronomy and Biotechnology, China Agricultural University, Beijing 100193, China, †National Energy R&D Center
for Biomass, China Agricultural University, Beijing 100193, China, ‡Center for Agricultural Resources Research, Institute of
Genetics and Developmental Biology, Chinese Academy of Sciences, Shijiazhuang 050022, China, §Center for Crop Systems
Analysis, Wageningen University, P.O. Box 430, Wageningen, AK 6700, The Netherlands
Abstract
Crop residue resources may affect soil quality, global carbon balance, and stability of crop production, but also
contribute to future energy security. This study was performed to evaluate the spatial and temporal variation inresidue quantities of field crops in five provinces of North China (NC) and three provinces of Northeast China
(NEC). The availability of biomass resources was derived from statistical data on crop yields for all crops on the
provincial and even county level.
We found that cereals – wheat, maize, and rice – were the biggest resource of crop residue feedstock. The
ranking of these crops as a source of biomass for bioenergy is determined by the acreage in each region and the
crop-specific yield. Annually, the average amount of total residue of 83.0 Mt (Mt = Mega tonnes) in NC
(16.9 Million ha) comprised 76.6 Mt field residues and 6.4 Mt process residues on an air-dried basis. The aver-
age amount of total biomass residue of 105.7 Mt in NEC (19.8 Million ha) comprised 92.8 Mt field residues and12.9 Mt process residues. Averaged for 2008, 2009, and 2010, the total standard coal equivalent (SCE) in NC
amounted to 46.4 Mt, which comprised 42.4 Mt field residues and of 3.9 Mt process residues. In NEC, the SCE
value of 57.0 Mt comprised 49.7 Mt field residues and 7.4 Mt process residues. The temporal availability of field
residues was mainly concentrated in the period between July and September, followed by the period between
October and December. In the period between July and September, the amount of field residue available
amounted to 40.9 and 53.1 Mt in NC and NEC, respectively. An accurate assessment of field residues may guide
policy makers and industry to optimize the utilization of the crop residue resource.
Keywords: availability for biofuel, crop residue utilization, field residue, process residue, regional and seasonal variation,
regional residue productivity
Received 12 May 2013 and accepted 4 June 2013
Introduction
The development of renewable energy to reduce the use
of fossil fuels and decrease of greenhouse gas (GHG)
emissions is of considerable interest nationally and glob-
ally. Bioenergy can play a significant role in meeting Chi-
na’s rapidly growing energy demand while substantially
reducing GHG emissions (Sang & Zhu, 2011). Non-food
feedstock ligno-cellulosic biomass has been used to pro-
duce biofuel, biogas, and solid fuel commercially in Chi-
na’s rural areas (Chen et al., 2009; Feng et al., 2009; Shen
et al., 2010; Zheng et al., 2010). Recently, the Chinese gov-
ernment has given a high priority to technology develop-
ment for producing liquid fuel (ethanol and butanol)
from cellulosic materials (Deng et al., 2008; Fang et al.,
2010; Wu et al., 2010; Qiu et al., 2012).
Crop residue has been recognized as an important
potential cellulosic feedstock due to its bulk of biomass
and not being in competition with food availability (Xie
et al., 2010). This article is one of our reports on the
assessment of crop residues in China. According to
China Statistics Yearbook (National Bureau of Statistics
of China, 2009, 2010, 2011), crop production in China has
been divided up into six regions. In this study, we ana-
lyzed the field crop residue feedstocks for biofuel in the
North (NC) and Northeast (NEC) region with an average
field crop area of 16.9 and 19.8 M ha, respectively, in the
period from 2008 to 2010 (National Bureau of Statistics of
China, 2009, 2010, 2011). The two regions differ in agro-
ecological conditions and in cropping patterns. North
China is dominated by maize–wheat cropping systems,
while in Northeast China rice and maize are the most
important crops in terms of land use.
1Lu Yang and Xiao Yu Wang contributed equally to this work.
Correspondence: Guang Hui Xie, tel. +86 10 62734850,
fax +86 10 62734851, e-mail: [email protected]
© 2013 John Wiley & Sons Ltd 1
GCB Bioenergy (2013), doi: 10.1111/gcbb.12109
Crop residue has been used for different purposes
such as fuel, feed, paper industry, substrates for mush-
room cultivation. It has also been recognized as a poten-
tial feedstock for biofuel (Liu et al., 2012). During the
last decades, various crop residue assessments for
China have been reported. However, due to inappropri-
ate definitions for crop residues and residue factors,
those reports exhibited a large variability in crop resi-
due quantities (Xie et al., 2010). Previous studies of our
group identified more accurate residue parameters for
all field crops based on sampling a total of 212 and 126
sites, respectively (Guo et al., 2012; Wang et al., 2012). In
earlier reports, maize residue mass was estimated
mostly by using a residue factor of 2.0 which was
derived from 23-year-old literature (Zhang & Zhu, 1990;
Xie et al., 2010). We reported that the field residue factor
varied between 0.93 and 1.30 depending on site (Wang
et al., 2012). In addition, we took maturity dates of main
field crops for different regions of China into account
(Wei et al., 2012a) to assess the seasonal distribution in
crop residue availability.
This article presents a detailed assessment of residue
quantities for all field crops for each province in North
China (NC) and Northeast China (NEC). The objectives
of this study are (i) to assess field crop residue quanti-
ties for all crops grown from 2008 to 2010 in the prov-
inces and counties of the NC and NEC regions; (ii) to
analyze the spatial and seasonal distribution in field
crop residue mass; and (iii) to assess the quantity of
crop residues available for biofuel production. The out-
come of the study aims at providing a quantitative
assessment of the potential of crop residues as a feed-
stock in bioenergy processing.
Materials and methods
Data collection
The data for field crops were derived from the China Statistical
Yearbook. The same applies for the data at the provincial level
(National Bureau of Statistics of China, 2009, 2010, 2011),
whereas the data at the county level were collected from the
Information Centre of Ministry of Agriculture.
The heat values, conversion factors, and crop maturity dates
for different crops were derived from literature (Guo et al.,
2012; Wei et al., 2012a). Data concerning the use of crop resi-
dues in the regions of NC and NEC (Fig. 1) were derived from
the literature published between 2002 and 2011. Microsoft Excel
2007 and GIS was used to manage data, perform calculations,
and mapping.
Calculations
Crop residues consist of the aboveground biomass left on a
field after the crop has been harvested. In the case of cereals it
will be straw, stover and stubbles; however, for sugar beet it
will be green leaves and heads of the harvested roots. The field
residue mass (FRM) of all crops on an air-dried basis with a
moisture content of 15%, except sugarbeet, was calculated
using Eqn (1). The data on the field residue of sugar beet are
presented as fresh weight in the China Statistical Yearbook; its
FRM was calculated using Eqn (2):
FRM ¼ ACP� FRI ð1Þ
FRM ¼ ACP� FRI� ð100�MÞ=100; ð2Þ
where FRM is the field residue weight of a field crop, ACP is
the average annual crop production, FRI is a field residue
index, and M is the moisture content, that is, 75% for
sugarbeet roots (Yu, 2003; Zhang et al., 2005). The field resi-
due index is defined as the ratio between field residue mass
and total aboveground biomass according to Wang et al.
(2012).
Process residue mass was assessed for five field crops. The
quantity of rice hull, maize cob, and peanut husk were esti-
mated using Eqn (3), whereas cotton seed hull was estimated
using Eqn (4), and sugarbeet bagasse Eqn (5). The equations
are as follows:
PRM ¼ ACP� PRI ð3Þ
PRM ¼ ACP� ð1=GOC� 1Þ � PRI ð4Þ
PRM ¼ ACP� PRI� ð100�MÞ=100; ð5Þ
where PRM is the process residue mass of a field crop, ACP
is the average annual crop production, PRI is the process resi-
due index defined as the process residue weight to crop pro-
duction ratio (Guo et al., 2012), GOC is the ginning outturn of
cotton at a value of 0.38 (Yu, 2003), and M is the moisture
content, which was 75% for sugar beet roots (Yu, 2003; Zhang
et al., 2005).
The potential energy value of field residues as biofuel was
assessed by calculating the standard coal equivalent (SCE). The
average annual SCE of each crop was derived from the heat
value and the conversion factor for the residue (Wei et al.,
2012b). Residue yield was the quotient of the total residue
quantity divided by the harvested area of each crop in each
province and region. Regional residue productivity (RRP) was
the total residue quantity divided by the area in each province
and region.
The average amount of soil amendments was derived from
the assessments of crop residues and of stubbles left after the
harvest. The latter was determined by field observations
carried out between 2009 and 2012.
The qualitative assessment on categorizing the feasibility of
field crop residues as feedstock for biofuel was mainly based
on five parameters: regional residue productivity (RRP), sur-
plus amount, harvest duration, traffic conditions, and crop suit-
ability to resource availability. These parameters turned out to
be appropriate for six regions in China. The symbol and the
number of ‘+’ represent the amount of residue available on the
county level of each province. The term ‘favorable crop’ was
used for the crop with the largest cultivated area in a province
or region.
© 2013 John Wiley & Sons Ltd, GCB Bioenergy, doi: 10.1111/gcbb.12109
2 L. YANG et al.
Results
Yields and densities of field crop residues
In the NC region, average annual yields of field resi-
dues varied between 1.5 and 6.1 t ha�1, while average
regional field residue productivity (RRP) varied
between 0.01 and 24.7 t km�2 among all field crops
from 2008 to 2010 (Table 1a). Maize, rice, wheat, and
sugar beet produced 5.2, 6.1, 5.4, and 5.9 t ha�1 of crop
residue, respectively. Maize and wheat showed residue
RRPs of 24.7 and 13.7 t km�2, respectively, much higher
than for any of the other crops. Among the provinces,
the highest RRP of field residue was found for maize,
ranging from 13.9 t km�2 in Inner Mongolia to
70.2 t km�2 in Hebei. The RRP of Beijing and Tianjin
were low, and the major reason was that Beijing and
Tianjin are urban areas. For Inner Mongolia, the value
was low due to the limited productivity per unit of land
on a huge area.
We also estimated the amount of process residues
for five crops: rice hull, maize cob, cotton seed hull,
peanut hust, and sugar beet bagasse (Table 1a). Wheat
bran was not taken into account. Maize cob residue
did not show the highest yield per ha, but had the
highest RRP at 3.3 t km�2. Rice hull was highest in
process residue yield per unit of land with an average
value of 1.1 t ha�1 for the whole region. Within the
region the yield of process residue ranged from 1.0
(Tianjin and Shanxi) to 1.3 (Inner Mongolia) t ha�1,
ane the residue densities ranged from 2.0 (Inner
Mongolia) to 16.7 (Tianjin) t km�2. On average, the
amount of process residues was less than 10% of the
field residues.
Among field crops in the NEC region, average annual
yields of field residues ranged from 1.7 (tobacco) to 6.6
(rice) t ha�1 and residue densities between 0.01 (Canola)
and 59.6 (maize) t km�2 (Table 1b). The RRP of beans
in Heilongjiang province was higher than in other prov-
inces and for other crops, reaching 38.0 t km�2. Rice
and maize showed the highest average field residue
densities: 31.6 and 59.6 t km�2, respectively. The field
residue yields of rice and maize amounted to 6.6 and
5.3 t ha�1. Like the NC regions, there were big differ-
ences between provinces in field residue yield and resi-
due densities. In both regions, NC and NEC, the
acreage of the crop is more important for the RRP per
region or province than the yield.
Process residue of maize cob showed an average
RRP of 9.6 t km�2. Among provinces and crops the
process RRP varied from 0.01 to 16.6 t km�2. Process
residue yields in these three provinces ranged from 1.0
to 1.6 t ha�1. Compared to the NC region process resi-
dues contributed relatively somewhat more; the
amount of process residues was about 13% of the field
residues.
Table 1a Annual yield and regional productivity (RRP) of field crop residues for provinces in North China (NC) averaged for the
years 2008 to 2010
Residue
type
NC Beijing Tianjin Hebei Inner Mongolia Shanxi
Yield RRP Yield RRP Yield RRP Yield RRP Yield RRP Yield RRP
(t ha�1) (t km�2) (t ha�1) (t km�2) (t ha�1) (t km�2) (t ha�1) (t km�2) (t ha�1) (t km�2) (t ha�1) (t km�2)
Field residue 4.4 49.8 5.3 76.0 4.8 153.6 4.6 173.7 4.6 19.5 3.4 67.5
Rice 6.1 0.8 7.8 0.9 9.0 12.1 6.3 2.9 5.5 0.5 2.8 0.02
Wheat 5.4 13.7 6.8 25.1 5.6 51.8 6.3 79.4 3.5 1.6 4.0 18.5
Maize 5.2 24.7 5.2 47.7 4.4 61.7 4.5 70.2 6.5 13.9 4.7 43.5
Beans 1.8 2.0 2.6 1.5 1.6 1.7 2.5 2.9 1.8 1.8 1.1 2.4
Tubers 1.5 1.1 2.7 0.5 1.7 0.1 1.5 2.0 1.7 1.0 0.8 0.9
Cotton 3.0 1.5 4.6 0.2 3.6 16.9 2.8 9.3 6.3 0.00 3.4 1.6
Peanut 2.9 0.8 2.9 1.0 2.8 0.2 3.0 6.3 1.7 0.03 1.9 0.1
Canola 2.6 0.4 3.7 0.4 2.5 0.5 3.1 0.1
Sugarbeet 5.9 0.2 5.1 0.3 6.0 0.2 6.7 0.2
Tobacco 1.8 0.01 1.5 0.02 2.2 0.01 1.7 0.04
Process residue 0.4 4.2 1.1 8.0 1.0 16.7 1.1 14.4 1.3 2.0 1.0 6.6
Rice hull 1.1 0.2 1.2 0.03 1.2 1.6 1.1 0.5 1.1 0.1 0.49 0.01
Maize cob 0.7 3.3 0.8 7.6 0.7 10.2 0.6 9.3 0.8 1.8 0.6 6.0
Cotton seed hull 0.9 0.4 1.4 0.1 1.1 5.0 0.8 2.7 1.8 0.01 1.0 0.5
Peanut hust 0.9 0.2 0.9 0.3 0.9 0.1 0.9 1.8 0.5 0.01 0.6 0.04
Sugarbeet
bagasse
2.1 0.1 1.8 0.1 2.1 0.1 2.3 0.1
© 2013 John Wiley & Sons Ltd, GCB Bioenergy, doi: 10.1111/gcbb.12109
A QUANTITATIVE ASSESSMENT OF CROP RESIDUE 3
Quantity of crop residue and its regional variation
The annual total amount of crop residue produced in
NC from 2008 to 2010 varied between 80.3 and
85.8 Mt (Mega tonnes; Table 2). This amount consisted
on average of 76.6 Mt field residue (92%) and 6.4 Mt
process residue (8%) (Table 3a). The total amount of
field residues among the five provinces ranged from
1.2 Mt in Beijing to 34.0 Mt in Hebei. The provinces
Hebei and Inner Mongolia contributed the largest part:
44.3% and 36.6%, respectively (Table 3a). The fractions
of field and process residue of the total residue
amount in the same province did not much differ
between years.
Maize produced the largest quantity of total residue
including 38.4 Mt field residue and 5.1 Mt cob resi-
due (Table 3a). Wheat had the second largest total
residue quantity at 20.7 Mt. Together, wheat and maize
accounted for approximately 77.2% of the total amount
of field residue. This ranking was mainly determined by
the acreages of the two most important cereal crops:
maize and wheat. The provinces of Shanxi and Inner
Mongolia contributed an amount of field residues of
11.5 and 28.1 Mt, respectively. Most of the variation in
crop residue production between provinces was due to
differences in acreage, yield, and cropping systems.
Process residues comprised for approximately 80% of
maize cob. The average annual production of process
residues in the five provinces varied between 0.1 (Beij-
ing) and 2.7 Mt (Hebei). The province of Hebei had the
greatest amount of process residues with 2.7 Mt, which
was mainly derived from maize cobs (Table 3a).
The spatial variation in total field residue mass
between counties in the NC region varied between 0
and 2.4 Mt per county (Fig. 2a). Of a total of 423 coun-
ties, only 19 had a field residue mass higher than
1.0 Mt, and 155 counties had a field residue mass
greater than 0.5 Mt. The counties with a field residue
mass higher than 0.5 Mt were mainly located in Hebei
(Fig. 3).
The annual average total residue biomass in the NEC
region was estimated at 105.7 Mt, composed of an aver-
age annual production of field residue and process resi-
due of 92.8 and 12.9 Mt, respectively (Table 3b). The
average annual amount of field residues varied between
17.7 Mt (Liaoning) and 46.8 Mt (Heilongjiang). In the
NEC region, maize field residues were highest, reaching
49.1 Mt (52.9%) (Table 3b). The two main cereal crops –
maize and rice – made up about 80.0% of the total
residue production.
The average annual production of process residues in
the three provinces varied between 2.6 (Liaoning) and
6.3 Mt (Heilongjiang) (Table 3b). Maize cob residue was
7.9 Mt and rice hull residue 4.6 Mt, which accounted
for 61.5% and 35.4% of the total process residue in this
region, respectively.
The annual field residue mass of field crops varied
between 0.6 Kt and 2.0 Mt among counties (Fig. 2b). Of
the 183 counties, there were 16 counties with a residue
mass greater than 1.0 Mt and 58 counties with a residue
Table 1b Annual yield and regional productivity (RRP) of field crop residues for provinces in Northeast China (NEC) averaged for
the years 2008 to 2010
Residue type
NEC Heilongjiang Jilin Liaoning
Yield RRP Yield RRP Yield RRP Yield RRP
(t ha�1) (t km�2) (t ha�1) (t km�2) (t ha�1) (t km�2) (t ha�1) (t km�2)
Field residue 4.7 113.2 4.0 222.3 6.0 57.6 5.2 108.9
Rice 6.6 31.6 5.8 74.4 8.5 12.3 7.9 35.2
Wheat 3.8 1.5 3.7 5.7 4.3 0.04 6.5 0.4
Maize 5.3 59.6 4.8 99.9 6.3 40.9 4.9 64.9
Beans 1.8 11.7 1.7 38.0 2.5 3.2 3.0 3.7
Tubers 1.9 1.1 1.6 2.3 1.7 0.4 2.9 1.8
Cotton 5.6 0.02 5.9 0.02 5.1 0.03
Peanut 1.8 1.0 1.7 0.3 2.3 0.6 1.6 2.9
Canola 3.6 0.01 3.0 0.03 6.4 0.02
Sugarbeet 4.3 0.4 4.1 1.4 9.3 0.1 5.4 0.1
Tobacco 1.7 0.2 1.5 0.3 2.0 0.1 1.8 0.2
Process residue 0.6 15.6 1.0 31.0 1.6 8.7 1.2 16.9
Rice hull 1.2 5.6 1.1 13.8 1.4 2.0 1.3 5.8
Maize cob 0.9 9.6 0.8 16.6 1.0 6.5 0.8 10.2
Cotton seed hull 1.6 0.01 1.7 0.01 1.5 0.01
Peanut hust 0.6 0.3 0.5 0.1 0.7 0.2 0.5 0.9
Sugarbeet bagasse 1.5 0.1 1.5 0.5 3.3 0.02 1.9 0.02
© 2013 John Wiley & Sons Ltd, GCB Bioenergy, doi: 10.1111/gcbb.12109
4 L. YANG et al.
mass greater than 0.5 Mt. The counties with a field resi-
due mass greater than 0.5 Mt were mostly located in
the southern part of Heilongjiang, the central part of
Jilin, or the northeast part of Liaoning (Fig. 3).
Seasonal variation in the amount of crop residues
The seasonal distribution of the amount of field residues
in the North China region exhibited the following order:
July to September (40.9 Mt) > October to December
(27.9 Mt) > April to June (7.9 Mt) (Table 4). No crop
residues were harvested from January to March. In
Inner Mongolia, crop residues were harvested in the
period between July and September and the period
between October and December. The total average
quantity of field residue from crops harvested in the
NEC region in the period between July and September
was estimated at 53.1 Mt (Table 4). The quantity of field
residues harvested in the period between July and Sep-
tember was 25.5 Mt in Heilongjiang, 16.6 Mt in Jilin,
and 11.1 Mt in Liaoning. The amount field residues in
the period between October and December were esti-
mated at 6.5 Mt in Liaoning, 11.7 Mt in Jilin, and
21.3 Mt in Heilongjiang. In Jilin province field residue
were only harvested in the period between July and
September and the period between October and Decem-
ber. There were no crop residues harvested from Janu-
ary to March.
The SCE value of field crop residues during the per-
iod between July and September amounted to 40.9 Mt
and 53.1 Mt in NC and NEC, respectively. The quantity
of field residue and its SCE in the period between Octo-
ber and December were 39.6 Mt (42.7%) and 21.1 Mt
(42.6%) in NC and NEC, respectively. More than 99% of
field crop residues were present in the period between
July and December because of the single cropping
system in NEC.
Standard coal equivalent of crop residues
The annual total SCE in the NC region amounted to
46.3 Mt, which comprised 42.3 Mt field residues and
3.9 Mt process residues (Table 5). Maize produced the
largest SCE equaling 50.1% of the total produced in this
region. Wheat produced the second highest SCE. SCE
values of field residues varied between 0.7 and 18.7 Mt
among the five provinces (Table 5). The annual SCE of
process residues per province ranged from 0.1 to
1.6 Mt, which corresponds closely to the relative contri-
butions of field residues. The SCE value of process
derived from maize cob was estimated at 3.1 Mt or 79%
of the total process residue.
The annual average SCE for field crops residue in
NEC was estimated to be 49.7 Mt for field residues andTab
le2
Quan
tity
andpercentageoffieldan
dprocess
residues
ofcropsgrownfrom
2008
to2010
inprovincesofNorthChina(N
C)an
din
provincesofNortheast
China(N
EC)
Reg
ionan
d
province
Field
residue
Process
residue
Totalresidue
2008
2009
2010
2008
2009
2010
2008
2009
2010
Amount
(106
t)
Percent
(%*)
Amount
(106
t)
Percent
(%*)
Amount
(106
t)
Percent
(%*)
Amount
(106
t)
Percent
(%*)
Amount
(106
t)
Percent
(%*)
Amount
(106
t)
Percent
(%*)
Amount
(106
t)
Percent
(%*)
Amount
(106
t)
Percent
(%*)
Amount
(106
t)
Percent
(%*)
NC
77.2
100
74.1
100
79.4
100
6.5
100
6.2
100
6.4
100
83.7
100
80.3
100
85.8
100
Beijing
1.3
1.6
1.3
1.7
1.2
1.5
0.1
2.0
0.1
2.10
0.1
1.9
1.4
1.7
1.4
1.7
1.3
1.5
Tianjin
1.7
2.2
1.8
2.4
1.8
2.2
0.2
3.1
0.2
3.24
0.2
2.8
1.9
2.3
2.0
2.4
1.9
2.3
Heb
ei34.0
44.1
33.8
45.6
34.4
43.3
2.8
42.7
2.7
43.2
2.5
39.6
36.8
44.0
36.5
45.5
36.9
43.0
Inner
Mongolia
28.7
37.2
26.6
35.8
12.7
16.0
2.3
35.9
2.2
35.4
1.1
17.6
31.0
37.1
28.7
35.8
31.8
37.1
Shan
xi
11.5
14.9
10.7
14.5
29.4
37.0
1.1
16.3
1.0
16.0
2.4
37.9
12.6
15.0
11.7
14.6
13.8
16.1
NEC
93.4
100
86.1
100
99.7
100
12.7
100
12.0
100
13.9
100
106.1
100
98.2
100
113.6
100
Heilongjian
g45.1
48.3
44.6
51.8
51.6
51.4
5.8
45.8
6.0
50.0
7.2
51.7
50.9
48.0
50.7
51.6
58.4
51.4
Jilin
29.3
31.4
25.4
29.5
30.2
30.3
4.2
33.2
3.7
30.4
4.1
29.3
33.6
31.6
29.1
29.6
34.3
30.2
Liaoning
19.0
20.3
16.1
18.6
18.3
18.3
2.7
20.9
2.4
19.6
2.7
19.0
21.6
20.4
18.4
18.8
20.9
18.4
*Thepercentagewas
calculatedforeach
province
within
aregionforeach
year.
© 2013 John Wiley & Sons Ltd, GCB Bioenergy, doi: 10.1111/gcbb.12109
A QUANTITATIVE ASSESSMENT OF CROP RESIDUE 5
7.4 Mt for process residues (Table 5). Crop residues pro-
duced in the three provinces of this region exhibited
SCE values ranging between 10.8 and 28.7 Mt (Table 5).
The SCE of process residues derived from maize cob
and rice hull amounted to 4.8 Mt and 2.2 Mt, account-
ing for 65.7% and 30.4% of the total process residue in
this region, respectively.
Discussion
Crop cultivation is influenced by agroecological, socio-
economic, and technological conditions (Inthavong
et al., 2001). The spatial distribution of field crop resi-
dues has significant regional characteristics as is shown
by the quantity and distribution of field crop residue
produced in the NC and NEC regions. This study pre-
sents a comprehensive assessment of the quantities of
field crop and process residues and their distribution in
the NC and NEC regions. These assessments are based
on statistical data for crop acreage and yields in 3 years
and crop-specific field and process residue indexes. The
variation in field residues was huge, not only in quan-
tity – ranging from 1.2 (Beijing) to 46.8 Mt (Heilongji-
ang) but also in RRP – ranging from 19.5 (Inner
Mongolia) to 222.3 t km�2 (Heilongjiang). The temporal
distribution of the availability of feedstock is character-
ized by the crop harvests in the period between July
and September and the period between October and
December. Most of the field residue feedstock becomes
available in the period from July to September: 60.7%
and 65.3% in the NC and NEC regions, respectively.
Table 3a Average annual amount of field crop residues in provinces of North China (NC) from 2008 to 2010
Residue
type
NC Beijing Tianjin Hebei Inner Mongolia Shanxi
Amount Percent Amount Percent Amount Percent Amount Percent Amount Percent Amount Percent
(103 t) (%*) (103 t) (%*) (103 t) (%*) (103 t) (%*) (103 t) (%*) (103 t) (%*)
Field residue 76591.5 100 1226.2 100 1740.7 100 34026.5 100 28068.3 100 11529.8 100
Rice 1263.3 1.6 2.7 0.2 146.1 8.4 529.6 1.6 581.2 2.1 3.7 0.03
Wheat 20737.5 27.1 396.2 32.3 617.5 35.5 14975.1 44.0 1847.4 6.6 2901.5 25.2
Maize 38375.5 50.1 768.2 62.6 753.0 43.3 13395.5 39.4 16308.3 58.1 7150.4 62.0
Other
cereals
4483.0 5.9 10.9 0.9 3.1 0.2 1074.3 3.2 2785.5 9.9 609.2 5.3
Beans 3034.1 4.0 21.9 1.8 22.1 1.3 518.3 1.5 2107.5 7.5 364.2 3.2
Tubers 1615.3 2.1 6.9 0.6 1.8 0.1 382.0 1.1 1091.0 3.8 133.7 1.2
Cotton 2092.8 2.7 2.8 0.2 189.1 10.9 1669.3 4.9 4.6 0.02 227.1 2.0
Peanut 1221.4 1.6 15.5 1.3 3.2 0.2 1156.1 3.4 28.0 0.1 18.6 0.2
Canola 655.9 0.9 80.2 0.2 556.7 2.0 19.0 0.2
Sesame 37.0 0.1 18.7 0.1 11.2 0.04 7.1 0.1
Other oil crops 2784.2 3.6 1.2 0.1 4.8 0.3 178.3 0.5 2530.7 9.0 69.3 0.6
Other fibers 71.1 0.1 0.4 0.01 70.7 0.3
Sugarbeet 197.7 0.3 42.9 0.1 135.8 0.5 18.9 0.2
Tobacco 21.4 0.03 4.6 0.01 9.8 0.04 7.1 0.1
Process residue 6412.5 100 128.3 100 199.1 100 2709.1 100 2311.4 100 1064.6 100
Rice hull 233.5 3.6 0.4 0.3 18.7 9.4 94.8 3.5 119.0 5.1 0.6 0.1
Maize cob 5103.0 79.6 122.2 95.2 124.0 62.3 1766.4 65.2 2108.8 91.2 981.4 92.2
Cotton seed hull 612.5 9.6 0.8 0.6 55.3 27.8 488.6 18.0 1.3 0.1 66.5 6.2
Peanut hust 356.6 5.6 4.9 3.8 1.0 0.5 336.1 12.4 8.8 0.4 5.8 0.5
Sugarbeet
bagasse
106.9 1.7 23.2 0.9 73.4 3.2 10.2 1.0
Total residue 83004.0 1354.5 1939.8 36735.6 30379.7 12594.4
*The percentage was calculated for different residues within a province or a region.
Fig. 1 Spatial distribution in North China and Northeast
China.
© 2013 John Wiley & Sons Ltd, GCB Bioenergy, doi: 10.1111/gcbb.12109
6 L. YANG et al.
(a) (b)
Fig. 2 Spatial distribution of the average field residue quantities for counties in North China (a) and Northeast China (b) for the
years 2008 to 2010.
Table 3b Average annual amount of field crop residues in provinces of the Northeast China (NEC) from 2008 to 2010
Residue type
NEC Heilongjiang Jilin Liaoning
Amount Percent Amount Percent Amount Percent Amount Percent
(103 t) (%*) (103 t) (%*) (103 t) (%*) (103 t) (%*)
Field residue 92804.3 100 46817.0 100 28312.6 100 17674.7 100
Rice 25856.1 27.9 15138.3 32.3 5673.6 20.0 5044.3 28.5
Wheat 1114.3 1.2 1044.1 2.2 16.8 0.1 53.4 0.3
Maize 49098.1 52.9 20626.5 44.1 18673.8 66.0 9797.7 55.4
Other cereals 3476.3 3.7 978.9 2.1 1187.6 4.2 1309.8 7.4
Beans 9155.8 9.9 7109.0 15.2 1522.5 5.4 524.4 3.0
Tubers 1093.8 1.2 551.1 1.2 261.8 0.9 280.9 1.6
Cotton 14.3 0.02 10.8 0.04 3.5 0.02
Peanut 900.7 1.0 48.5 0.1 294.1 1.0 558.1 3.2
Canola 7.2 0.01 5.0 0.01 2.2 0.01
Sesame 27.8 0.03 4.0 0.01 20.3 0.1 3.6 0.02
Other oil crops 1232.4 1.3 578.5 1.2 584.6 2.1 69.3 0.4
Other fibers 510.9 0.6 504.3 1.1 6.6 0.02
Sugarbeet 185.7 0.2 168.0 0.4 11.9 0.04 5.7 0.03
Tobacco 130.9 0.1 60.8 0.1 48.3 0.2 21.9 0.1
Process residue 12881.1 100 6341.1 100 3986.8 100 2553.1 100
Rice hull 4566.3 35.4 2797.3 44.1 936.4 23.5 832.5 32.6
Maize cob 7927.5 61.5 3437.8 54.2 2948.5 74.0 1541.2 60.4
Cotton seed hull 4.2 0.03 3.2 0.1 1.0 0.04
Peanut hust 282.8 2.2 15.2 0.2 92.3 2.3 175.2 6.9
Sugarbeet bagasse 100.4 0.8 90.8 1.4 6.4 0.2 3.1 0.1
Total residue 105685.4 53158.1 32299.4 20227.8
*The percentage was calculated for different residues within a province or a region.
© 2013 John Wiley & Sons Ltd, GCB Bioenergy, doi: 10.1111/gcbb.12109
A QUANTITATIVE ASSESSMENT OF CROP RESIDUE 7
Though there are different residue types in different
regions or provinces, the same pattern in distribution
was found (Liao et al., 2004; Elmore et al., 2008; Liu
et al., 2008; Jiang et al., 2012). We found that cereals
were the biggest resource of crop residue feedstock:
wheat and maize in the NC region and rice and maize
in the NEC region. The ranking of these crops is deter-
mined by the acreage in a specific regions and the crop
residue yield. This finding can be used to validate the
scaling up of the geospatial distribution of field residues
in China (National Bureau of Statistics of China, 2009,
2010, 2011). Second favorable crop for the NC region
was soybean, rice for Tianjin, millet for Shanxi, and
potato for Inner Mongolia. In the NEC region, the
second favorable crop was soybean.
Crop residues have traditionally been used as a soil
amendment, as material for cooking and heating in farm
households, as raw material and as animal feed. Reten-
tion of crop residue is essential for carbon sequestration,
maintaining soil quality and reducing the risk of soil
erosion. Indiscriminate removal of residue can lead to a
decline in soil quality, with long-lasting adverse impacts
on the environment. However, some researchers suggest
that all residues incorporated into the soil may not meet
the demands of soil erosion control and quality mainte-
nance (Lu et al., 2009).
We found that, between 2002 and 2011, the quantity
of crop residue in the NC region needed for soil
amendments was 33.8 Mt (44.1%) and the quantity to
be used for biofuel was 24.4 Mt (31.9%) (Table 6a).
These data do not include crop stubbles. Through our
research program, it was shown that the stubble
weight fraction of field residues was 0.085, which cor-
responds to 6.5 Mt of field residues allocated to the
soil. Previous reports estimated the average percentage
of crop residues needed for soil amendments and the
percentage available for biofuel in the NEC region
were 22.7% and 59.0%, respectively (Table 6b). The
amount of field residue for biofuel was estimated to be
23.1 Mt in Heilongjiang, 18.6 Mt in Jilin, and 10.9 Mt
in Liaoning.
The economic feasibility of crop residues as feed-
stock for biofuel depends on: regional residue produc-
tivity; costs of collecting, loading, transportation of the
feedstock, and other related costs (e.g., storage) for bio-
energy production (Brechbill et al., 2011). The feasibility
of crop residues for biofuel use has also some limita-
tions, mainly because of its variability in physicochemi-
cal properties and in supply (Dai et al., 2008; Callej�on-
Ferre et al., 2011). For instance, the field crop residues
have poor energy characteristics (low RRP, low heating
value, and sometimes a relative high-moisture content)
causing high costs during transportation, handling, and
storage (Virmond et al., 2012). Moreover, some
researchers indicated that excessive residue use for bio-
energy might cause negative effects on soil quality and
crop yield (Jiang et al., 2012). The feasibility of crop res-
idues for biofuel production is influenced by many fac-
tors, such as yield, RRP, harvest dates, soil fertility
(Zhang et al., 2005), traffic, and field conditions (Bi
et al., 2008; Liu et al., 2008, 2012; Li et al., 2010; Sun
et al., 2010; Wei et al., 2012b). We illustrated that crop
acreage and yield of cereals are quantitatively the most
important factors. Besides, the availability of crop resi-
Table 4 Seasonal distribution of the amount of field residues and its standard coal equivalence (SCE) for provinces in North China
(NC) and Northeast China (NEC) averaged for the years 2008–2010
Period
NC region NEC region
NC Beijing Tianjin Hebei
Inner
Mongolia Shanxi NEC Heilongjiang Jilin Liaoning
Apr.~
Jun.
Amount (103 t) 7852.3 365.4 608.2 5739.8 0 1138.9 60.0 0.3 0 59.7
(%*) 10.3 29.8 34.9 16.9 0 9.9 0.1 0.001 0 0.3
SCE (103 t) 4278.4 198.7 331.4 3130.6 0 617.7 26.1 0.2 0 25.9
(%*) 10.1 29.4 34.5 16.7 0 9.7 0.1 0.001 0 0.3
Jul. ~
Sept.
Amount (103 t) 40867.3 432.9 473.4 19000.7 15139.9 5820.4 53132.6 25473.2 16563.8 11095.6
(%*) 53.3 35.3 27.2 55.8 53.9 50.5 57.2 54.4 58.5 62.8
SCE (103 t) 22558.6 240.2 256.5 10454.4 8379 3228.5 28486.3 13721.3 8944.9 5820.1
(%*) 53.3 35.5 26.7 55.8 53.8 50.6 57.3 54.7 62.5
Oct. ~
Dec.
Amount (103 t) 27871.9 427.9 659.1 9286.0 12928.4 4570.9 39611.7 21343.5 11748.8 6519.4
(%*) 36.4 34.9 37.9 27.3 46.1 39.6 42.7 45.6 41.5 36.9
SCE (103 t) 15495.8 237.0 372.1 5161.2 7191.6 2533.8 21152.4 11367.0 6315.7 3469.8
(%*) 36.6 35.1 38.8 27.5 46.2 39.7 42.6 45.3 41.4 37.2
Total Amount (103 t) 76591.5 1226.2 1740.7 34026.5 28068.3 11529.8 92804.3 46817.0 28312.6 17674.7
SCE (103 t) 42332.8 675.9 960.0 18746.2 15570.6 6380.0 49664.8 25088.5 15260.6 9315.8
*The percentages were calculated for the field residue amount and its SCE in different periods within a year.
© 2013 John Wiley & Sons Ltd, GCB Bioenergy, doi: 10.1111/gcbb.12109
8 L. YANG et al.
Fig. 3 Frequency distribution of the annual average field residue quantities of each county in provinces of North China (NC) and
Northeast China (NEC) for the years 2008 to 2010.
© 2013 John Wiley & Sons Ltd, GCB Bioenergy, doi: 10.1111/gcbb.12109
A QUANTITATIVE ASSESSMENT OF CROP RESIDUE 9
dues should also be evaluated by taking some more
qualitative factors, such as harvest duration or traffic
conditions on a county or province level into account
(Table 7).
The amount of crop residues and its availability for
biofuel could be explored on a local, regional, and
national level by developing an algorithm that takes
into account biomass quantity, energy value, acreage,
transportation distances, and weather conditions.
Trade-offs with other competitive factors, such as
alternative uses of crop field residues (feed, soil
organic matter, soil cover, etc.), should also been taken
into account by local and national authorities and pri-
vate companies.
Table 5 Annual standard coal equivalent (SCE) of field crop residues for provinces in North China (NC) and Northeast China
(NEC) averaged for the years 2008–2010
Residue type
NC Beijing Tianjin Hebei Inner Mongolia Shanxi
SCE Percent SCE Percent SCE Percent SCE Percent SCE Percent SCE Percent
(106 t) (%*) (106 t) (%*) (106 t) (%*) (106 t) (%*) (106 t) (%*) (106 t) (%*)
Field residue 42.4 91.5 0.7 89.6 1.0 89.0 18.7 91.9 15.6 91.6 6.4 90.7
Process residue 3.9 8.5 0.1 10.4 0.1 11.0 1.6 8.1 1.4 8.4 0.7 9.3
Total residue 46.4 100 0.8 100 1.1 100 20.4 100 17.0 100 7.0 100
Residue type
NEC Heilongjiang Jilin Liaoning
SCE (106 t) Percent (%*) SCE (106 t) Percent (%*) SCE (106 t) Percent (%*) SCE (106 t) Percent (%*)
Field residue 49.7 87.1 25.1 87.5 15.3 86.8 9.3 86.5
Process residue 7.4 12.9 3.6 12.5 2.3 13.2 1.5 13.5
Total residue 57.0 100 28.7 100 17.6 100 10.8 100
*The percentages were calculated for standard coal equivalent of different field residues within a province or a region.
Table 6a Calculated annual utilization and surplus quantity of field residues of field crops for provinces in North China (NC)
Region
and provinceNC Beijing Tianjin Hebei Inner Mongolia Shanxi
Parameter
Amount
(106 t)
Percent
(%)
Amount
(106 t)
Percent
(%)
Amount
(106 t)
Percent
(%)
Amount
(106 t)
Percent
(%)
Amount
(106 t)
Percent
(%)
Amount
(106 t)
Percent
(%)
Soil
amendment*
33.8 44.1 0.4 32.4 0.7 44.1 23.1 68.0 8.2 29.1 5.4 47.0
Fodder 13.0 17.0 0.1 10.3 0.3 17.0 1.5 4.3 9.3 33.2 2.3 20.0
Household
fuel
11.8 15.4 0.3 27.0 0.3 15.4 3.2 9.5 6.5 23.3 0.2 1.8
The other
uses
5.4 7.0 0.02 1.8 0.1 7.0 2.0 5.8 0.6 2.2 2.1 18.5
Surplus† 12.6 16.5 0.3 28.5 0.3 16.5 4.2 12.4 3.4 12.2 1.5 12.7
Total‡ 76.6 100 1.2 100 1.7 100 34.0 100 28.1 100 11.5 100
Availability
for biofuel§
24.4 31.9 0.6 55.5 0.6 31.9 7.4 21.9 9.9 35.5 1.7 14.5
Referencee Liu et al., 2012;
Zhang et al.,
2010; Niu et al.,
2011; Gao et al.,
2009; Yan et al.,
2005; Kang et al.,
2007
Zhang
et al., 2010
Liu et al., 2012;
Zhang et al.,
2010; Niu et al.,
2011; Gao et al.,
2009; Yan et al.,
2005; Kang et al.,
2007
Niu et al.,
2011; Gao
et al., 2009
Liu et al., 2012 Yan et al., 2005;
Kang et al.,
2007
*Including stubble weight for which we conducted field surveys to collect data between 2009 and 2012.
†Surplus refers to the crop residue burned and abandoned.
‡The total percentage means a sum of the percentage of soil amendment, fodder, household fuel, the other use, and surplus.
§The sum of household fuel and surplus residue; e: Reference for the utilization percentages within a province or a region.
© 2013 John Wiley & Sons Ltd, GCB Bioenergy, doi: 10.1111/gcbb.12109
10 L. YANG et al.
This assessment of field and process residues may
guide policy makers and industry to optimize the utili-
zation of the crop residue resource. We suggest further
studies on field residue quantity assessment, crop resi-
due collection, maintaining soil quality, and the social
and economic risks.
Acknowledgements
This study was supported by Chinese Universities ScientificFund (Project No. 2012QJ131). We gratefully acknowledge
Dr. Qingquan Chu for presenting the crop production data ofcounty level.
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