Document Type : Research Paper
M.Sc., Student, Agriculture Mechanization, Ferdowsi University of Mashhad
Assoc. Prof., Department of Farm Machinery Engineering, Ferdowsi University of Mashhad -Iran
M.Sc., Mechanics of Agricultural Machinery, Ferdowsi University of Mashhad -Iran
Energy and environmental issues are two common concerns of modern societies. Fossil fuels consumption is believed to be the primary factor contributing to severe environmental problems, such as global warming, climate change and acid rain, which are a serious threat to the world’s ecosystems. In order to stabilize the earth’s climate and prevent further global warming, the earth requires a 70% cut in present carbon dioxide emissions by 2050. In the executive summary of IEA (2006), it claims “Beyond 2020, the role of renewable energy in global energy supply is likely to become much more important”. Among these, biomass can be defined as all the biological materials produced and existing within an ecological system and as sources of renewable energy can be converted directly into energy or energy carrier materials.
Regarding to biomass assessment, researchers estimated the sustainable energy potential of biomass resources in Thailand including: (i) agricultural residues, (ii) animal manure, (iii) fuel-wood saving potential through improvement of efficiency, (iv) possibility of fuel-wood saving through substitution by other fuels, (v) municipal solid wastes, and (vi) wastewater. The potential of each source was estimated for the reference year 1997 and for the years 2005 and 2010. The total energy potential of these sources in 1997, 2005 and 2010 were 525, 702 and 821 PJ, respectively. In Iran, Khorasan Razavi province is known as an important region of biomass production in the country including: crops, livestock and poultry. Hence, in this study the potential of biomass and its distribution were evaluated.
Materials and methods
In the present study, the collectable residue has been estimated that is known as None Gross Yield (NGY), using two factors, which are Harvest Index (HI) and Gross Yield (GY). Harvest index factor (%), defined as follow:
HI= (Biological yield / Product yield) × 100 (1)
Biological yield is defined as all parts of the crop including grain and straw. Harvest index is not constant as it is dependant of several factors mainly climate and crop type and cultivation. Therefore, the average harvest index of each crop has been used that were obtained by Agriculture and Natural Resources Research Center of Khorasan Razavi and the other research centers through the country and other parts of the world. The data is presented in Table 1.
Table 1: Average harvest index of important crops in Khorasan Razavi Province
Using Equation 2, the None Gross Yield (NGY) of any product can be estimated:
(2) /HI GY. (1-HI) NGY=
Since the roots and a fraction of the stems of plant remain in the soil (except sugar beets, tomatoes and melons), 15 percent of NGY was deducted. Thus, the recoverable residue that is produced can be calculated as follows:
Collectable agricultural residues = NGY- (NGY × 0.15) (3)
To assess the Collectable agricultural residues of important crops in Khorasan Razavi province (wheat, barley, sugar beet, cotton, melon and tomato), statistics related to Gross Yield (GY) for six years (2004- 2010) were extracted from the records of Agriculture Organization of the country. Consequently, the average annual productions of these crops were calculated. Using the data of Table 1 and also considering GY per unit of crops and according to Equation 2, Residue-to-Product Ratio (RPR) which also known as Waste Factor for each crop was calculated. Having this, and using Equation 3, the average annual collectable agricultural residue was estimated. At the end, the Average energy value of each of these waste crops was extracted from various research sources. Thus the Average annual energy potential of these wastes was evaluated that are presented in Table 3.
In order to assess the collectable manure potential and their energy content for heavy livestock in the province, the relevant data was integrated that are presented in Table 4. Considering the factors including: livestock breeds, types, number, percentage of the manure and based on the average live weight of the animal that has been extracted from the ASAE Standard D384.1 FEB03, the amount of produced fresh manure per cow were calculated, for the reference year 2009. This procedure was followed for the total number of livestock in each city of Khorasan Razavi province. According to ASAE D384.1 FEB03 dairy cows, heifers and beefs produce manure about 6.8%, 2.6% and 8.5% of their live weight per day, respectively. The average weight of each animal in the study area was then calculated. The average weight of livestock (cattle) was extracted according to the breed and animal type that are present in Table 2.
Table 2: The average weight of livestock
Average weight (kg)
In Khorasan Razavi province, there were 5791211 and 1080224 sheep and goats respectively, in 2009. In order to evaluate the potential of lightweight animal manure, the average weight of sheep and goat were considered as 55 and 40 kg, respectively. According to ASAE D384.1 FEB03 Standard, these animals produce 4.0% and 4.1% of their live weight manure per day, on average. Thus, using the average weight of animal and the ASAE D384.1 FEB03 Standard, the potential of livestock manure that can be collected for three months of the year has been calculated which is presented in Table 4.
Broilers’ farming is performed periodically (averagely four periods per year) and after each period the average weight of broilers reaches 2.5 kg. During the period each broiler consumes approximately 5.56 kg of feed from which in average 25% is converted to manure (1.4 kg). In Khorasan Razavi province, the capacity of the poultry farms is about 17064420 units. Thus, to calculate the number of broilers per year, the capacity of the poultry farms multiplied by the number of periods per year (four periods) and from the total, 5% is deducted as average losses of the farms. Then the resulting number is multiplied by 1.4 kg.
Finally, the potential of the manure from this sector, for the base year 2009, was evaluated in Khorasan Razavi province which is shown in Table 4.
The capacity of farms in the province, for layers was about 7774747 units in 2009. Normally, in a growing period, only two-third of the capacity is used for poultry and also 3% of the capacity is considered as losses. Therefore, according to what is mentioned above, first the number of poultry was calculated. Thereafter, using the average weight of poultry at the end of period (1700 g) and the conversion factor for manure from ASAE D384.1 FEB03 Standard equal to 6.4%, the total potential of this manure was evaluated (Table 4).
Results and conclusions
The results of this study showed that,with consideration of the sum of biomass crops, livestock and poultry in the province of Khorasan Razavi, according to Tables 3 and 4, the province's energy potential is estimated to be 47.3 PJ (equivalent to approximately 8 million barrels of oil).Also, among the cities of KhorasanRazavi province, Neyshaboor, Mashhad, Torbate jam and Sabzevar were determined as the main areas of biomass production and diversification. But in term of biomass density (ton per km2) production, Jovein, Joghatay and Neyshaboor will be ranked in top positions, respectively.
Table 3: The annual average energy potential of agricultural crop residues in Khorasan Rrazavi province
Annual production (103 ton)
Annual average of crops production (103 ton)
Annual average of residues production (103 ton)
Energy value of residues (GJ/ton dry matter)
Annual average energy of residues (PJ)
Dry matter %
Dry land wheat
Dry land barley
Dry land melon
Table 4: Assessment of energy potential of collectable livestock and poultry manure in Khorasan Razavi province in 2009
Average weight of animal (Kg)
Wet manure production Kg/head/day
Average of total solids
Average of volatile solids
Potential of manure production (103 ton)
Biogas yield (m3/Kg VS)
Amount of biogas