In fact, the white-haired Michigan woman looks very much what she is: a grandmother and farmer's wife.
But on April 19, Henning became one of the 2010 winners of the Goldman Environmental Prize, sometimes called the Green Nobel, the largest prize in the world given to grass-roots environmentalists.
How she became a self-taught bane to local CAFOs (concentrated animal-feeding operations) is a story 10 years in the making.
"What struck the jury was that her leadership addressed one of the most serious and least-talked-about issues in our country today," says Lorrae Rominger, deputy director of the Goldman Prize in San Francisco.
This is the first time the $150,000 prize has been awarded to someone battling CAFOs, Ms. Rominger says. The jury was very concerned about "the water and air pollution that comes from these factory farms and how they are making people sick," she says.
Many Americans are unaware of the environmental costs of industrial-style farming, Rominger says. "I just don't think that many people understand there are factory farms in this country where they keep thousands of animals in a barn with no windows."
Henning says she once had been content just farming.
"I stayed home with my kids. I raised all my own food in my own garden," she recalls while taking a reporter on a tour of local CAFOs, casually pointing out where a creek runs red with bloodworms.
A former sign painter, she has spent much of her life helping her husband on their 80-acre farm in Clayton, a small town in south-central Michigan. "We lived the American dream until the CAFOs came to town," Henning says.
Today, 20,000 cows are within a 10-mile radius of her home, she says, and another 20,000 hogs cycle through on an annual basis. (Before the CAFOs, there were about 500 animals in the same area, she says.)
Waste from one cow equals that produced by 23 humans. That waste (along with whatever else is on the barn floor) is washed into lagoons that hold millions of gallons, where it is stored for months before being spread on fields.
The smell, even in early March, is nearly overpowering. "It's industrial agriculture using family farms as a disguise," Henning says. "Manure is no longer manure – it's toxic waste." And it needs to be treated as such, she says, not spread untreated on fields or allowed to wash into local water sources.
This is not what most Americans think of as farming. "They think of a little red barn. They don't think of 5 million gallons of manure – not the 6,000 pigs that never see the light of day," says Dave Maturin, a county commissioner and real estate appraiser. He cites instances of Michigan homes losing 30 to 60 percent of their value after a CAFO moved in. In some cases, he says, homeowners can't sell at any price.
For Henning, keeping her windows open in summer isn't really an option any more, she says. She can't hang laundry on the line or sit outside without checking which way the wind is blowing – or leave her front door open. Eating outside is largely a thing of the past.
"I used to love spring," Henning says. Now, "I hate spring."
Henning became concerned about CAFOs a decade ago, after a neighbor accused her in a grocery store of filing a complaint against a local CAFO operator. She hadn't, but her curiosity was piqued. She started filing federal Freedom of Information Act requests, and as she learned more she became more alarmed.
Then in 2003, her in-laws, who had farmed in Clayton their whole lives, were diagnosed with hydrogen-sulfide poisoning. Their doctor said it was his opinion that the poisoning came from the local cow husbandry operations and manure lagoons.
In 2000, Henning and other local residents founded a group, ECCSCM (Environmentally Concerned Citizens of South Central Michigan), to monitor the CAFOs. In 2005, Henning was hired as a water sentinel for the Sierra Club.
"We could either fight or pack up," she says. "We've been here too long to leave."
With the help of Light Hawk, a volunteer group of pilots, ECCSCM has taken aerial photos of CAFOs since 2001. The flights have led to 1,077 reported violations. The state of Michigan has collected more than $1.4 million in fines from CAFOs in south-central Michigan.
In 2008, State Line hog farm was shut down after ECCSCM found that the surrounding air quality had up to 9 parts per million of hydrogen sulfide. "Ten parts will cause unconsciousness," Henning says dryly.
Despite these victories, Henning says not enough has changed. "I think it's going to get worse before it gets better," she says.
The impact of Henning's prize is "going to be exponential," says John Klein, a cofounder of ECCSCM who takes the aerial photos. Some of the prize money will be used to buy an air-quality monitor.
"Lynn has done this in an amazing way," says Anne Woiwode, state director of the Sierra Club. "She just has always been there quietly pursuing, taking notes, asking questions, and learning how to do what needs to be done, whatever it is."
Henning frequently files complaints on behalf of other residents so that they can remain anonymous, Ms. Woiwode says. "She's taken on the role of protector, because she knows how bad it is, and she doesn't want other people to have to go through that."
Henning matter-of-factly recounts a list of harassments and lawsuits against her that stretches back for years: Being chased by manure tankers down the road; having dead animals left in her driveway and car; and having her mailbox blown up.
On Dec. 30, someone shot out the window of her granddaughter's bedroom with buckshot. The 2-year-old was in the room at the time.
Environmentalists are sometimes accused of being antifarming, but Henning says she's different.
"They have a hard time with me because I am a farmer," she says. "I drive a tractor."