**Table 2.**

*Emission factor of the national grid (tCO2 / MWh) in Brazil (2000–2015).*

*Biogas Generation from Bovine Confinement: An Energy Policy Option for Brazil DOI: http://dx.doi.org/10.5772/intechopen.99828*

However, the use of biogas produces GHG emissions, as indicated by Gómez et al. [28]. According to IPCC, the burning of biogas results in CH4 and N2O emissions, which are considered by subtracting them from the reduction. The standard values supplied by Gómez et al. [13] of 1 and 0.1 kg GHG/TJ biogas for methane and nitrous oxide, respectively, were used. These values will be considered in the final calculation of total emissions in each of the scenarios proposed in the article.

In the case of emissions avoided using biogas, the result is the difference between the emissions generated during the beef production process, irrespective of the system, discounting the emissions avoided using biogas as electricity. Then, emissions with the use of biogas are given by the following:

$$\mathbf{E}\_{\text{błąga}} = \left(\mathbf{g}\_{\text{błąga}} \ast F\mathbf{E}\_{\text{CH4}} \ast F\mathbf{C}(T\mathbf{I})\right) / 1000 + \left(\mathbf{g}\_{\text{błąga}} \ast F\mathbf{E}\_{\text{N2O}} \ast F\mathbf{C}(T\mathbf{I})\right) \tag{2}$$

where:

Ebiogas = biogas burning emission, in tCO2e, gbiogas = biogas generation potential, in MW. FECH4 = methane emission factor with the use of biogas (1 kg/TJ). FC(TJ) = conversion factor from TJ to MWh (0,003599712). FEN2O = nitrous oxide emission factor with the use of biogas (0,10 kg/TJ). For emissions abated with biogas, the equation is represented by:

$$\mathbf{E}\_{\text{abat}} \stackrel{\text{bògas}}{=} \mathbf{g}\_{\text{bògas}} \ast \mathbf{f}\_{\text{grid}} \tag{3}$$

where:

Eabatbiogas = emission abated using biogas in tCO2e,

gbiogas = biogas generation potential, in MW.

fgrid = grid emission factor, in tCO2/MWh (see **Table 2**).

So, the final abated emissions (EFbiogas) using biogas are given in the formula:

$$EF\_{\text{błogas}} = \mathbf{E}\_{\text{abat}}{}^{\text{błogas}} - \mathbf{E}\_{\text{błogas}} \tag{4}$$

To analyze the impact of increased confinement times and rates due to the use of biogas for the generation of energy for the agricultural sector and the reduction in GHG emissions, three different intensification scenarios are proposed, in addition to the reference one. One with the increased confinement time, another with the elevated confinement rate, and finally joining all the scenarios for the intensification of livestock raising through confinement.

### **4. Scenarios**

### **4.1 Reference scenario**

In this scenario, from 2016 until 2030, an average growth rate equal to all the variables seen in the 2000–2015 period is proposed.

In the reference scenario, confinement rates will follow the linear growth tendency observed between 2000 and 2015. In other words, semi-confined cattle will grow at an average annual rate of 0.35%, equal to the growth observed in the

period, 9.7%, and confined cattle at an average annual rate of 4,9%, with a growth of around 51.4% occurring during the period. At the same time, the same hypothesis of linear growth of confinement will be applied to both the size of the beef herd and the number of animals slaughtered in the country. In the case of the beef herd, during this period there was an increase of around 1.6% per year (21.4% in the period as a whole) and in the number of slaughtered animals a little less than 1% per year (13.4% between 2000 and 2015).

As **Table 3** shows, the number of heads of cattle confined will rise from a little over four million, in 2015, to just over 8.2 million in 2030. By 2030, the number of semi-confined heads of cattle will be a little over 2.8 million, while in 2015, there were around 2.7 million. If we compare the number of heads with some type of confinement in relation to the total heads of the beef herd, the more intensive beef production system rises from almost 3.5%, in 2015, to 4.5%, in 2030. Finally, the total cattle herd, without dairy cows, will rise from almost 193.5 million, in 2015, to a little more than 246.2 million in 2030.

In relation to slaughter, the values range from a little above 41 million head of cattle in 2015, to around 47.4 in 2030. The demand for energy for the beef slaughter process will rise from 1600.3 GWh to around 1847.1 GWh (**Table 3**).

### **4.2 Scenario 1: increase in confinement time**

From 2016 until 2030, in relation to the reference scenario, in scenario 1 confinement time increases from 4 to 6 months, and from 2 to 3 months for semiconfinement. The only change in relation to the reference scenario is the confinement time.

The increase in confinement does not result in changes to the initial values calculated for the reference scenario. For this reason, the values of numbers of heads of confined, semi-confined, slaughtered, and total cattle, demand for energy remain the same, as described in **Table 3**. This parameter will alter the potential of the generation of biogas, as will be observed in the results, and consequently the emissions presented reduced somewhat the total emissions generated by animal slaughter over the years, with these small changes in emissions being observed in relation to the reference scenario in the results present in the next item.

### **4.3 Scenario 2: increase in the confinement rate**

In the period 2016–2030, in scenario 2 there is an increase in the rate of cattle with some type of confinement from the rate seen in 2000–2015, rising from 3.5% to 10.9% by 2030, an annual rise of around 9.7%. This hypothesis will allow the rate of cattle with some type of confinement to reach by 2050 the minimum rate practiced in some countries, such as Australia, or as seen in the state of Texas in the US, of approximately 50% in relation to the total beef herd.

With this, as shows, the value of confined and semi-confined cattle will be altered, and the others maintained in accordance with the calculations made for the reference scenario. Since the confinement rate does not indicate the type of confinement, the hypothesis used to calculate the number of confined and semi-confined cattle from 2015 onwards was the average rate of confined and semi-confined cattle in relation to the total cattle with some type of confinement between 2012 and 2015. The reason for this hypothesis is the tendency for these rates to stabilize in recent years, with little variation, as seen in **Figure 4**.

Between 2012 and 2015, the average of this rate for confined cattle was around 59.4%, with an oscillation lower than 2%, also seen in semi-confined cattle.

