Annex 2. Method of calculating the value presented in table 2 for the efficiency of naoh energy usage

The MJ of NaOH energy input per MJ additional energy stored as body-weight gain was calculated as follows.

1,000 kg untreated straw provided for

1,000 kg treated straw provided for

In 222 days a calf fed untreated straw also consumed

222 x 0.8 = 178 kg oilcake

In 167 days a calf fed treated straw also consumed

167 x 1.0 = 167 kg oilcake

In 222 days a calf fed untreated straw gained

222 x 0.25 = 55.5 kg

In 167 days a calf fed treated straw gained

167 x 0.42 = 70.0 kg

Therefore, the treatment of straw increased weight gain by 70.0 - 55.5 = 14.5 kg/1,000 kg straw. (This figure is conservative, because a calf fed treated straw consumed slightly less oilcake/1,000 kg straw than the one fed untreated straw.) The energy value of this bodyweight gain is taken as 9.6 MJ/kg (calves about 1-year-old gaining at a rate of 0.40 kg/day[19]), or 139.2 MJ for 14.5 kg. The manufacturing energy cost of NaOH is estimated to be 51 MJ/kg;

1,000 kg straw x 3.3 kg NaOH/100 kg x 51 = 1,683.