Global beer brewer SABMiller launched its first ever cassava-based beer on Tuesday, an affordable beer category aimed at cracking the untapped home brew market in the world's poorest continent.

The first Cassava beer will be brewed in Mozambique.

By using Cassava -- a drought resistant root vegetable rich in starch -- to brew beer, SABMiller will be commercialising a technique used by Africans for generations to brew beer at home.

We estimate that the volume of the informal, unregulated alcohol market across Africa could be up to four times that of the formal market, said Mark Bowman, managing director of SABMiller's African operations.

Bowman expects the new brand -- Impala Cerveja -- to contribute about 10 percent of its annual sales in Mozambique over the next two to three years.

Mozambicans consume around 8 litres of beer per capita each year, excluding beer brewed at home, suggesting that there's still plenty of room for growth because in other countries such as South Africa where the annual consumption rate per capita is 60 litres.

Impala could fetch up to 70 percent of the mainstream beer market thanks partly to a new Mozambique law which reduces the excise rate for beers made from the cassava, the company said.

SABMiller said it would use about 40,000 tonnes of raw cassava each year in the production of Impala from more than 1,500 smallholder farmers.

SABMiller's Africa region, excluding South Africa, saw the fastest growth in underlying beer volumes, up 15 percent, of all its regions in its half-year to end-September.

(Reporting by Tiisetso Motsoeneng; Editing by Marius Bosch)