**2. Biogas produced from cattle confinement as a complementary and strategic energy resource in Brazilian energy policy**

According to the FAO [11], it is estimated that livestock emit around 7.1 GgCO2eq per year or 14.5% of total global emissions. The same study demonstrates that most emissions are related to the production of beef (41%) and milk (20%). Emissions are also linked to the production and processing of animal feed, enteric fermentation, the handling of waste and the remnants of processing, and the transport of products of an animal origin [11]. In the Brazilian case, in the last inventory, emissions related to enteric fermentation accounted for 11,158 GgCH4 or around 66.9% of total methane emissions in the country in 2010 and in the case of animal waste, this value was 3.6% of total methane emissions, 608.1 GgCH4 [12].

Confinement can contribute to the generation of electric energy with lower GHG emissions. This reduction is due to the conversion of methane generated during the beef production process into biogas as a source of energy for the energy sector, slaughterhouses, and abattoirs in particular, part of the highly energy intensive agricultural sector. At the same time, as it is a system with higher production costs in relation to the extensive system3 , biogas also contributes to reducing these costs. The **Figure 3** shows how the confinement rate in Brazil is still very low.

Biogas is a gaseous mix produced by the anaerobic decomposition of organic material whose characteristics and typical composition, according to Persson et al. [14], is around 53–70% methane and 30–47% carbon dioxide, with

<sup>3</sup> Feeding the beef cattle herd in Brazil is based on pasture, the most economic and practical means of feeding cattle. This contribute to the lower costs of beef production which are competitive in relation to the United States, Australia, and various European countries. In the latter, the predominant system is confinement, dependent on other economic factors which oscillate, such as variations in the prices of grains or fossil fuels [3, 7–10, 12, 13]. The generation of biogas help to minimize the costs associated with confinement.

### *Bovine Science - Challenges and Advances*

**Figure 3.**

*Participation of cattle in confinement system and cattle in extensive system or rational grazing system on the total Brazilian cattle herd, 2000-2015. Source: Prepared by the authors, based on FNP (2002, 2005, 2012 and 2016).*

traces of at least 1000 ppm of sulfuric acid and at least 100 ppm of ammonia. Agricultural waste treatment systems are principally responsible for the use of the anaerobic digestion process [15].

Biogas is widely used in some countries, such as China and India, for cooking and lighting in rural areas. In Brazil, the use of this energy source was intensified in the 1970s, through governmental programs in small rural properties to reduce the dependence on LPG and the negative impacts of raising animals, as well as to increase the income of landowners. However, the lack of technical knowledge to construct and operate bio-digesters was one of the principal problems of the use of biogas in the country [16–18]. Usually, the most common uses of biogas, seen in a wide variety of countries, is its use for heating and the generation of electricity. In the case of the use of biogas for electricity generation, various technologies are available, with the principal applications being gas turbines and internal combustion generators [19].

The generation of biogas from animal waste depends on different factors: temperature, pH, alkalinity, the characteristics of animal waste, and how it is handled in the production system. As a result, animal diet gives the waste distinct potentials to produce gas [16–18]. The production of biogas is possible with the confinement of cattle before slaughter and from effluents from the production process in slaughterhouses and abattoirs.

Two types of confinement are practiced in Brazil [12]. Confinement and semi-confinement during the dry periods of the year, from May/June to October/ November. For the confined cattle, the fattening period lasts on average four months, and two for semi-confined. **Table 1** shows the growth of the confinement system in the country in recent years. In 2000, the number was 4.39 million, of which 55.6% were semi-confined and 44.4% confined. In 2015, it reached a little more than 6.7 million, with approximately 40.3% being semi-confined cattle and almost 59.7% confined. In the 2000–2015 period, there was an increase of 34.6% [20–23].

The largest producers of beef in the world, the United States and Australia [24], have an average rate of confined cattle of around 50%, some years some US states, such as Texas, have an even higher rate. In the Brazilian case, this rate was 3.5% in 2016. Few states had rates much higher than the national average, notably São Paulo with 4.8% of the national herd and a confinement rate of 10.4% of its total herd. However, in many states there is little or no confinement though they have, at the same time, a large share of the national herd, as is the case of the state of Pará with approximately 10.1% of the total of the national beef herd in 2015 and



with less than 1% of the cattle in the state being confined. This panorama shows the possibility of expanding beef cattle confinement in Brazil in comparison with the rates of confinement in some Brazilian states, but above all in various other countries.

The greater economic competitiveness of the extensive pasture system in relation to the intensive one with confinement can be compensated by the increase of beef production and the reduction of costs through the production of a new energy source (biogas), as well as the reduction in the emissions produced using this source of energy, and a lower dependence on electricity by the agricultural sector. Biogas can thus be an interesting and strategically positive energy policy.
