A process for the preparation of expandable polylactic-acid-containing pellets, comprising the steps of: a) Melting and incorporation by mixing of the following components: i) from 65 to 95% by weight, based on the total weight of components i to iii, of polylactic acid, where the polylactic acid consists of: ia) from 65 to 95% by weight of polylactic acid with content of from 0.3 to 5% of D-lactic acid and ib) from 5 to 35% by weight of polylactic acid with content of from 10 to 18% of D-lactic acid; ii) from 5 to 35% by weight, based on the total weight of components i to iii, of an aliphatic polyester selected from the group consisting of polybutylene succinate, polybutylene succinate-co-adipate and polybutylene succinate-co-sebacate; iii) from 0 to 2% by weight, based on the total weight of components i to iii, of a compatibilizer; and iv) from 0.1 to 5% by weight, based on the total weight of components i to iii, of an additive, b) incorporation by mixing of v) from 1 to 7% by weight, based on the total weight of components i to iv, of an organic blowing agent and vi) from 0.01 to 5% by weight of a co-blowing agent - selected from the group of nitrogen, carbon dioxide, argon, helium and mixtures thereof - into the polymer melt by means of a static or dynamic mixer at a temperature of at least 140°C, c) discharge through a die plate with perforations, the diameter of which at the die outlet is at most 1.5 mm, and d) underwater pelletization of the blowing-agent-containing melt directly downstream of the die plate at a pressure in the range from 1 to 21 bar. a) Melting and incorporation by mixing of the following components: i) from 65 to 95% by weight, based on the total weight of components i to iii, of polylactic acid, where the polylactic acid consists of: ia) from 65 to 95% by weight of polylactic acid with content of from 0.3 to 5% of D-lactic acid and ib) from 5 to 35% by weight of polylactic acid with content of from 10 to 18% of D-lactic acid; ii) from 5 to 35% by weight, based on the total weight of components i to iii, of an aliphatic polyester selected from the group consisting of polybutylene succinate, polybutylene succinate-co-adipate and polybutylene succinate-co-sebacate; iii) from 0 to 2% by weight, based on the total weight of components i to iii, of a compatibilizer; and iv) from 0.1 to 5% by weight, based on the total weight of components i to iii, of an additive, i) from 65 to 95% by weight, based on the total weight of components i to iii, of polylactic acid, where the polylactic acid consists of: ia) from 65 to 95% by weight of polylactic acid with content of from 0.3 to 5% of D-lactic acid and ib) from 5 to 35% by weight of polylactic acid with content of from 10 to 18% of D-lactic acid; ii) from 5 to 35% by weight, based on the total weight of components i to iii, of an aliphatic polyester selected from the group consisting of polybutylene succinate, polybutylene succinate-co-adipate and polybutylene succinate-co-sebacate; iii) from 0 to 2% by weight, based on the total weight of components i to iii, of a compatibilizer; and iv) from 0.1 to 5% by weight, based on the total weight of components i to iii, of an additive, b) incorporation by mixing of v) from 1 to 7% by weight, based on the total weight of components i to iv, of an organic blowing agent and vi) from 0.01 to 5% by weight of a co-blowing agent - selected from the group of nitrogen, carbon dioxide, argon, helium and mixtures thereof - into the polymer melt by means of a static or dynamic mixer at a temperature of at least 140°C, v) from 1 to 7% by weight, based on the total weight of components i to iv, of an organic blowing agent and vi) from 0.01 to 5% by weight of a co-blowing agent - selected from the group of nitrogen, carbon dioxide, argon, helium and mixtures thereof - into the polymer melt by means of a static or dynamic mixer at a temperature of at least 140°C, c) discharge through a die plate with perforations, the diameter of which at the die outlet is at most 1.5 mm, and d) underwater pelletization of the blowing-agent-containing melt directly downstream of the die plate at a pressure in the range from 1 to 21 bar.