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Significance
Livestock rearing is a common practice globally. It’s obvious that such popularity will keep on growing credit to all the products that are obtained from livestock. In fact, this livestock husbandry development industry has morphed from a makeup of mostly small-scale households into one of large-scale commercial production for agricultural sustainability. Concurrently, there has been a steady increase of livestock excrement comprised of dung and urine. This substantial increase in excreta has raised grave concern regarding severe environmental pollution. Agricultural consumption of excrete as manure (via composting and recycling anaerobically) has over the years declined due to its labor intensiveness and low nutrients per volume when compared to artificial fertilizers. Livestock excrement (LE) accumulation generates odors, ammonia, and dust that can exceed safety standards and tolerable levels. Even worse, it can lead to nitrates accumulations that over the years percolates and pollutes ground water. On the other hand, it is well known that anaerobic digestion offers an efficient way to recycle LE and create renewable energy, i.e., biogas while mitigating global warming potential. On this account, much research has been undertaken to determine the biogas output potential for China. Unfortunately, majority of published literature either under- or overestimated LE production and distribution in China hence providing inclusive data that is vital for planning and policy making.
Therefore, a comprehensive assessment of the quantity and distribution of livestock excrement (LE) production could significantly promote contamination control methods and biogas development in China. Bearing this in mind, researchers from the China Agricultural University: Mr. Weiqing Bao (MSc student), Dr. Yang Yang, Dr. Tongcheng Fu (PhD students) and led by Professor Guang Hui Xie, conducted in-depth investigation using the latest assessment of LE production in this series based on updated findings. Their goals were to evaluate LE production from 2007 to 2015 for all livestock types in China, illustrate LE distribution in the six regions and 31 provinces of China, estimate the LE biogas production potential in 2015, and forecast LE production and biogas potential in 2030. Their work is currently published in Journal of Cleaner Production.
To begin with, the researchers collected husbandry production data. Next, the researchers calculated LE production and its biogas potential. They then collected coefficient values for LE calculations following which a scenario analysis of LE production and commercial scale husbandry growth in 2030 was undertaken. Simply put, the team assessed LE and its biogas potential by using the latest updated LE definitions and calculation coefficients, for 14 types of livestock according to China’s husbandry statistics data.
The study revealed that LE increased by 10.9% from 1563.2 metric tons (Mt) in 2007 to 1755.0 Mt in 2015 at a rate of 12.3% in fresh weight and increased by 12.8% from 367.1 Mt to 414.5 Mt in dry weight. Among the six regions, from 2013 to 2015, the LE was distributed in ascending order in the Northwest, Northeast, Southwest, North, Central-south, and East regions on a dry weight basis. The average LE produced among the 31 provinces in China was seen to range widely from just 0.8 Mt (Shanghai) up to 42.4 Mt (Shandong), with the latter having the highest LE density distribution (275.7 t km-2) on a dry weight basis.
In summary, the study by China Agricultural University scientists successfully investigated LE production in China while as the same time assessing its potential for biogas production. Generally, the researchers reported that the east-middle provinces: i.e. Liaoning, Shandong, Henan, Hebei, Tianjin, Jiangsu, and Anhui, exhibited relatively higher levels of LE density distribution (111.2-275.7 t km-2) than those of other regions. The researcher further reported that the scenario analysis undertaken predicted that by the year 2030, the annual LE from CSHF could range from 201.1 to 258.9 Mt, corresponding to biogas potential of 86-111 billion m3. In an interview with Advances in Engineering, Professor Guang Hui Xie, the lead author pointed out that their work brought to light the country’s potential for biogas through effective LE management.
Reference
Weiqing Bao, Yang Yang, Tongcheng Fu, Guang Hui Xie. Estimation of livestock excrement and its biogas production potential in China. Journal of Cleaner Production, volume 229 (2019) page 1158-1166.
