It wasn't the first time the 62-year-old Fresno native had seen a frosty, clear morning turn into a long, sooty drive in the San Joaquin Valley.

WHERE THERE'S SMOKE: A seemingly harmless burning of debris, such as this in the foothills east of Stockton, can add to the particle pollutants that trigger asthma and other respiratory problems. (Mark Crosse / The Fresno Bee)

"I had asthma as a kid," says Marsella. "There's got to be something we can do about this air. I thought it was getting better until I smelled this."

Farm burning touches a nerve with many residents.

Open-field burning of farm prunings, weeds and crop waste anywhere near a major road is hard to miss. People with sensitive lungs complain they know immediately when the burning takes place. Runny noses, persistent coughs, irritated lungs and doctor visits seem to follow.

Over many years, agricultural fires have developed a bad reputation, say San Joaquin Valley Air Pollution Control District officials who hear complaints.

"The chances of smoking out a community if a farmer burns on a no-burn day are quite high, and it happens," says Stephen Shaw, air quality project planner for the district.

So why do the air pollution cops even allow burning? Because the state allows it.

Authorities have historically allowed the burning of crop waste and prunings under a permit program because it's the cheapest way for growers to dispose of the farm and waste wood – generally called biomass.

The permits also allow farmers to burn the thin paper trays used in drying the raisin harvest.

Compared to driving on unpaved roads and other farming activities, ag burning is not a major source of particulates, according to air district figures. Officials say the soot and ash amount to 3% of the particulate pollution on a daily basis.

That is fewer than 10 tons a day, averaged over a year. For comparison, wood stoves and wood burning in fireplaces put out about 12 tons a day if averaged over a year. The dust from unpaved roads accounts for about 72 tons a day.

But those numbers mean nothing if an open-field ag burn smokes out your home, neighborhood or business.

Much of the burning takes place when the Valley's bowl of air is relatively clean, usually in the late fall and winter, though there is some burning in warm months.

The air district has employees who search for violators on no-burn days. In 2000, they cited 348 illegal burns for a total of $99,000 in penalties.

The average penalty was $285 to $300. An offender can go to a "burn school" – which provides education, much like traffic school for those who get tickets – and have a penalty reduced by $150. Thereafter, however, the penalties increase.

The Valley is the largest air district in the country. Eight counties from San Joaquin to Kern cover 25,000 square miles, and sometimes illegal burns are not seen.

BURNING DEBATE: A farmer uses a loader to move an orchard that has been cut into a pile to burn south of Kingsburg. Ag burning is permitted by the state, but the smoke can be overwhelming for those who live nearby. (Mark Crosse / The Fresno Bee)

The district is divided into three areas – north, central and south. At times, the air is clear enough for burning around Stockton, but not in the central area around Fresno or the southern area around Bakersfield.

In that case, the northern area burns, but the central and southern do not. So farmers in the central and southern areas pile up their crop wastes and wait for a clear day.

To deal with backlog, the air district is changing the burning regulations to carve the district into about 100 small zones. Burning would be stopped only in the small zones where the air is not good, allowing others to burn.

The backlog can be a problem. In Kern, Tulare, Fresno and Madera counties, the combined total of woody waste – such as orchard prunings – is more than 1 million tons annually.

No matter how well burning is managed or how much money it saves, some people want it stopped.

Dwayne Burk of Fresno wrote The Bee in January:

"It makes no sense to burn, period. Mulch and sell it. Use it for fuel for something productive. We need to stop this abuse of our air before it is no longer fit to breathe."

There are other, higher-priced options, such as using the waste for composting, livestock feed and animal bedding. But those options are not broadly attractive in a business that has struggled recently.

Electricity production seemed like the perfect answer in the 1980s when state and federal governments were heavily promoting it. More than a dozen biomass plants sprung up and began burning farm vegetation to make electricity.

It is far better for the air. Field research in 1997 showed that controlled biomass combustion was about 95% cleaner than open-field burning.

But, like the other alternatives, the idea has not flourished because of expense. It costs more to produce electricity with biomass or vegetation than it does with natural gas. And it is expensive for farmers to have the waste hauled to a biomass plant.

Several of the plants that opened in the 1980s quickly died off.

A handful of biomass plants in the Valley have been riding the highs and lows, some closing for years at a time and reopening when economics were more suitable.

During the energy crisis last year, a few plants fired back up. One was Sierra Power Corp. in Terra Bella.

The owners continue to wait for state officials and the utilities to help them get a long-term contract.

Sierra Power owner Kent Duysen says he can't keep his doors open without some certainty:

"It cost us $800,000 to start up again after being shut down six years. I think we're done for good if we shut down again."