「我が社は、社是に基づき、企業活動と地球環境との調和を目指し、積極的に環境保全に取り組み、良き地球市民として社会責任を果たします。」という一文を英訳するなら、

In conformity with our Company Motto, our Company is constantly striving to secure harmony between our corporate activities and the global environment; to approach the issue of protecting the environment in a positive manner; and thereby to fulfill our social obligations as an outstanding global citizen.

が適切です。