Here's my advice to anyone planning to write a job description and hire a sustainability coordinator. There are three main competencies I would look for, from technical to general:
TECHNICAL KNOWLEDGE RELATED TO SUSTAINABILITY
Do they know enough about sustainability science and frameworks to give you good advice, develop a credible framework, make decisions based on a reputable framework? At a minimum, I would want them to know about the UN SDGs and Global Reporting Initiative, and familiarity with The Natural Step and industry-specific certifications would be helpful. Some familiarity with the science behind climate change, chemical exposure, renewable energy and urban planning may be helpful.
Do they have experience with processes to get sustainability formalized within your organization: Sustainability planning, metrics, setting meaningful goals, and facilitating steering committees. For government, a familiarity with public meeting laws and related ethics and political processes would be helpful. Are they a good leader, facilitator, and team builder?
CHANGE MANAGEMENTDo they know how to persuade people, make persuasive business cases for projects, deal with nay-sayers, get people engaged and excited? Can they work effectively with stakeholders inside and outside the organization (and perhaps have any existing relationships that could be helpful)? Can they effectively move responsibility for sustainability into the systems of the organization (eg, planning, budgeting, standard operating procedures, performance reviews) such that the effort is not dependent upon their presence in the organization?
For more information on the competencies of sustainability coordinators/directors, go to the International Society of Sustainability Professionals. They conducted a competency study for people in this role and also have two levels of professional certification based on that research. You can search for certified professionals by city or country. Realize this certification was released in the last couple years but the number of professionals with one of these certifications is growing rapidly.