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Evaluation of prospects and barriers of biogas produced from livestock waste towards sustainable developmentand adaptation to climate change in Nghe An province, Viet Nam

The livestock sector is one of the fastest growing agricultural subsectors in Viet Nam, resulting in growing demand to sustainably dispose or re-use livestock waste. This research examined the current adoption of biogas digestion of livestock waste treatment at household farms in order to provide insights for policy towards effective implementation. A questionnaire survey was conducted in September 2019, with the participation of 120 livestock owners in Nghe An province, which focussed on accessing their perspectives on biogas and examination of factors impacting their decisions to utilize this technology. Most respondents determined biogas to be an attractive solution for improving the environment. However, several factors limited the development of biogas installation, including technical and financial barriers, awareness and capacity limitations, and financial support as the most significant of these. Government support and policies that encourage household biogas utilization as a sustainable energy source to combat climate change is recommended.


INTRODUCTION
The livestock sector plays a dominant role in the Vietnamese agriculture industry, accounting for 28% of agricultural gross value (Tung, 2017)  Company (Dac, 2020). Lake water turned black, alongside reports of strong odours from the pollution of pig slurry. Another example from Do Luong district reported damage to 142,000 m 2 of rice land, 42,000 m 2 of fishponds and contamination of drinking water in 16 households in the commune attributed to the waste effluent from the large-scale pig-breeding farm of Thai Duong Limited Company (Hoan, 2011   Livestock is an important and growing sector in Nghe An province, with the recent growth rate of livestock numbers estimated to be 5% to 5.5% per year. The province has more than 500,000 households producing livestock and poultry (Nghe An GSO, 2019). As of May 2019, total buffalo and cow numbers were estimated at 272,970 and 471,029 heads, respectively. While the total herd of pigs were two-fold higher, at 857,490 heads.

Questionnaire survey
In September 2019, a questionnaire survey was conducted of 120 livestock households from three neighbouring districts of Nghe An province: two delta districts (Dien Chau and Quynh Luu) and one middle mountainous district (Nghia Dan).
Trained investigators visited each district and carried out personal interviews with randomly selected households, rather than requesting that respondents complete the surveys on their own. This methodology was chosen on account of the higher accuracy of responses and completion rates compared to the latter. The questionnaire survey focused on the perspectives of households on using biogas digestion for livestock waste treatment and their knowledge on the benefits of biogas technology. Identifying factors that influence household decisions to adopt biogas technology were also included.

An province
In general, pig production in Nghe An province can be divided into industrial and smallholder farms. Industrial farms have at least 20 sows or 100 fatteners, and heavily invest in production, whilst smallholder farms operate on a much smaller scale (i.e., 1-9 heads). In 2015, there were 174 industrial farms located mainly in the delta districts, which jointly kept about 30% of the total pig herd of the province (Nghe An PC, 2015). The remaining 70% of the total pig herd belongs to smallholder farms (households), which are more vulnerable to swine diseases due to less hygienic farmyard conditions due to inadequate slurry removal. Biogas utilization could be an effective solution for smallholder farms to cope with this issue.
The delta districts had the highest number of biogas digesters of the different districts, whereas the high mountainous districts had the lowest (Figure 3). The ratio of biogas to pigs in the delta districts was also higher compared to the moutainous districts, which could be due to the higher pig population in the delta districts accounting for 54.5% of total pig numbers in the whole province (Nghe An

Characteristics of the livestock households
The response rate of the questionnaire survey was 100%. In total, the team collected primary data

10% of respondents received a primary degree.
Survey results indicate the main income from biogas households was from cultivation (35%), followed by service-trade and business (34%) and lastly from livestock raising mainly pig production (31%).
Monthly household income ranges from 2 million to over 10 million VND, with 39% of respondents earning 2-4 million VND, and 31% earning 4-6 million VND. Twenty-eight households had a monthly income of over 6 million VND, and only three of them an income of over 10 million VND.   Studies by (Roubík, Mazancova, Banout, & Verner, 2016) and (Vu, Tran, & Dang, 2007) reach similar conclusions in other parts of Viet Nam.

Perspectives of households using biogas digestion for livestock waste treatment
Most respondents used biogas for cooking only (95%), with only a small group using biogas energy for both cooking and lighting (5%). Typically, most biogas cooking devices are handmade or not brandnamed, with inefficient burning of cooking stoves leading to large volumes of gas wasted. As described in a study in Hue City and Hanoi Capital, Viet Nam, the biggest problem found on farms was the low quality of biogas devices. Gas cookers rusted very quickly and were unusable after 2-4 years (Cu et al., 2012).
Seventy-four respondents (61.6%) supplied surplus biogas (if any) to their neighbours; whereas the remaining 35.8% burned off excess biogas or released the gas into the atmosphere (2.6%). It is important to note that respondents expressed their interest in using surplus gas to power electricity generators.
The residue of biogas digestion, bio-slurry, can be used as fertilizer for crop production and aquaculture. Nutrients in bio-slurry, especially nitrogen, are more readily available than in manure, leading to a larger short term fertilization effect. However, only 35% of respondents use this by-product of biogas digestion for crop fertilization because they have backyard or cultivated land nearby. 65% of respondents do not use the by-product because they either doubt the benefits (25%), have no cultivated land (30%) or have difficulty in transporting liquid biogas slurries (10%). Similar findings reported that 33% of surveyed farmers used solid parts of digestate as fertilizers for rice, and the use of liquid parts was very limited due to long distances between biogas digestions and rice fields (Hynek, Jana, Le, & Jan, 2018). From the perspective of farmers, a lack of transport vehicles/devices were considered primary barriers of bio-slurry utilization, which was also confirmed in other studies in Viet Nam (Vu, Vu, Jensen, & Sommer, 2015), Tanzania (Jackson & Mtengeti, 2005) and Uganda (Bos & Kombe, 2009).

Examine the barriers of biogas development and solutions to overcome the issues
Most households (78%) declared positive impacts from biogas adoption. The investment cost followed by livestock population were the most important factors influencing the decision of livestock owners to install biogas digesters.
Other factors, such as availability of land for biogas digester construction, the type and size of livestock, the benefits in pollution reduction and production of energy also contributed to farmers' decisionmaking, significantly. This statement is also recognized in many rural areas in Viet Nam (Cu et al., 2012) and in Cambodia (Phanthavongs & Saikia, 2013 who provided detailed guidance throughout the project implementation. We also extend our sincere gratitude to many stakeholders who participated in the project.