Born in Columbia, South Dakota, Buntrock began learning about business working for his father, Rudy Buntrock, who managed the International Harvester farm equipment dealership, hardware store, and Standard Oil Bulk Station. At an early age, Dean showed signs that he was an entrepreneur by raising his own chickens and growing potatoes to sell to local restaurants. In 1952, during the Korean War, Dean went into the army. He attended finance school at Fort Benjamin Harrison. After he was discharged, Dean went back to St. Olaf College (where the current student center, Buntrock Commons, is named after him) and graduated in 1955. In 1956, when Dean's father-in-law died, Dean was brought to manage the family business. The company at that time operated 12 garbage trucks and had revenues each year of $750,000. Dean quickly realized the largest profits were in the disposal of garbage. Buntrock formed a national association for waste management and served as its first president.
In 1968, Dean combined his company with Wayne Huizenga's and Larry Beck's disposal companies. Their merger formed Waste Management, Inc. After going public, the company saw tremendous growth over the next 20 years. In the early 1970s, Waste Management, Inc. grew to a worldwide waste disposal company operating in 21 countries. They provided clean water, clean energy, and environmental consulting services, as well as the waste disposal service which earned them revenues of over $10 billion. In 1993, the name of the company was changed to WMX Technologies.
Dean Buntrock donated ~$36 million to St. Olaf college, the largest single gift ever made to St. Olaf or any other Lutheran college in the United States. The money was used as the lead gift to build the new student center which opened on November 5, 1999 and was named Buntrock Commons in honor of Dean and his family.
In 2002, Dean Buntrock, as well as the other officers of Waste Management Inc., were indicted by the Securities and Exchange Commission. The charges were multiple counts of fraud from 1992 through 1997. According to the SEC, the defendants falsified documents and misrepresented Waste Management's financial results to enrich themselves as well as keep their jobs. The matter was settled out of court in 2005 with no admission of wrongdoing.