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1. What they Made

2. How they Made it

3. Where they Made it

How Fertilzer was Made: Processes and Equipment

Dry Mixing involved combining three primary plant nutrients: Nitrogen/ Phosphate /Potassium, otherwise known as NPK, bagging them, and shipping them out. Mixed-type fertilizers can be combined with or without chemical reaction while ‘Complex’-type fertilizers always involve chemical reactions. One difficulty with Dry Mix was something called ‘settling’ whereby the three materials would separate if they were not the exact same size of granulation. Fertilizers were sold by grade—a value assigned to each of the three nutrients and measured by weight. After an early scandal in the industry, inspectors periodically checked the grade of individual batches, and if the Mixed ferstilizer had settled, you could get a different grade reading than advertised. To combat this, manufacturers put the materials through a process called ‘screening’ to ensure efficient and complete combining. Screening would usually remove any clumps or clods and prepare the materials to be mixed in a large mixing vat. After the combination, the fertilizer was conveyed in buckets, weighed and bagged, and either stored or shipped out.

The production flow at Central Chemical probably followed the traditional process for Mixed fertilizers and used the common types of equipment. The materials are brought in either by truck or train, and then stored in large wood-walled and concrete floored storage bins until needed. The materials were then moved by front loader to a bucket-type elevator and conveyed to theScreener . After being screened, the materials were then batched intoa large rotary or drum mixer. After mixing, the materials were conveyed either into storageor directly prepared for shipping. If they were stored, they materials might be rescreenced before beingweighed, bagged. In an alternate scenario, the materials might be delivered directly into a truck or application machine and applied directly by the operator.

The following description of a typical “dry-mixing” operation between 1920 and 1950 provides an explanation of the new form assumed by the plant:

“Solid materials … were shipped to the plants by rail in box cars. The materials were unloaded by hand or by a gasoline-powered lift-hopper truck. In the smaller plants the materials were still dumped into a “Georgia buggy,” a two-wheeled cart equipped with large-diameter wheels and a wooden box….

“The dry-mixing operation consisted of weighing the desired proportions of the different materials, crushing, and then mechanically mixing them either in a rotary drum or passing them through a stationary gravity mixer where the dry materials were simply fed in at the top through a series of baffles. To decrease caking, the mixed materials were stored from 10 days to several weeks to permit chemical reactions among the ingredients. The caked, cured material was broken up and passed through a 6-mesh screen before bagging. The burlap bags (later cotton bags) came in several sizes….

Sometime after 1937 the company, now called the Central Chemical Corporation, began mining limestone in the northern potion of the site. During the first half of the twentieth century, it was common for fertilizer companies to add materials to fertilizer simply to add weight. A large part of the weight of mixed fertilizers during the 1920-1950 period consisted of materials containing no nitrogen, phosphates, or potash. Adding inert fillers like sand, cinders, and sawdust was common. Also common was the addition of nonprimary nutrient materials like gypsum, limestone and dolomite. The practice of adding such fillers to fertilizer mixes was especially common in the South. If Central Chemical was using the limestone in this way, it was only the first of a series of ways that the company began to cut corners.

Around the same time that it began mining, Central Chemical began blending pesticide materials in addition to its fertilizer dry-mixing operation. Before World War II a handful of fertilizer companies in the Mid-Atlantic states began incorporating lead arsenate into fertilizer mixes. Central Chemical may have been one of these companies; both arsenic and lead have been detected in the soil around the plant. In the 1940s many fertilizer companies began incorporating weed killers and chlorinated hydrocarbon insecticides into their fertilizer mixes. By 1943 the company was manufacturing “farm sprays.” Among the hydrocarbons used at Central Chemical were DDT, BHC (benzene hexachloride), chlordane, methoxychlor, aldrin, and dieldrin – all of which would eventually contaminate the entire site.

In fact, the decision to begin producing pesticides resulted in a series of disasters. The first was in 1943, not long after production of insecticides began, a devastating fire leveled the 1911 building and destroyed much of another building of later construction. The massive buildings visibly shook as chemicals exploded within.

Led by then-President Franklin Thomas, Central Chemical rebuilt the plant and continued with the production of fertilizers and insecticides. The new plant occupied a footprint similar to that of the 1911 building, but now featured a conveyor to carry materials from the railroad to a tower where they could be distributed to appropriate bins within the factory. If it was typical of other dry-mix plants of the period, it also used gasoline-powered carts for unloading the box cars, bucket elevators, and hopper cars.

By 1962 the plant had expanded dramatically . The fertilizer plant lost its conveyor on the north, but otherwise remains the same. Many new warehouses, however, were built in the northern section of the site (now labeled as “Insecticide Manufacturing” on the Sanborn maps). It is not clear how these buildings were used, and most of them are no longer standing. This period was apparently the high-water mark of the Hagerstown Central Chemical plant.

Then came more calamities. Just twenty years after the first fire, the company suffered two more disastrous fires – one in the fertilizer section in 1963 and a larger one in the air-mill grinding facility of the insecticide section in 1965. President Franklin Thomas II indicated that the affected area was dedicated to exports and government contracts. The fire chief remarked that “a pile of mixed DDT gave us the most trouble.” After this third fire, the company pulled the plug on the insecticide operations at the Hagerstown plant.

As Central Chemical turned away from insecticides to focus on dry-mixed fertilizers, the dry-mixing industry was declining in importance. In 1955, dry-mixed fertilizers accounted for 68% of the total consumption in the United States. By 1980, dry-mixed fertilizers accounted for only 35%. Farmers were increasingly deciding to bypass the factory mixing process altogether. Instead they began to purchase directly many of the same materials that supplied Central Chemical (nitrogen solutions, ammonia, superphosphates, urea, etc.) and would apply these directly to the soil. The use of direct-application fertilizer materials by farmers increased from 29% in 1955 to 52% in 1980.

The dry-mixing operations, themselves, were changing in response to pressures justify their place in the distribution system. During the 1960s most of the old dry-mix operations switched to a way of buying and mixing materials called “bulk blending.” Under this system, fertilizer companies bought granular materials, rather than in dry pulverized form, directly from primary producers. No inert fillers were used. The blending process was extremely simple. Costs of entry (plant and machinery) and of operation were quite low. After mixing the granules according to the proportions desired, the bulk blender would sell the product in bulk directly to farmers. Since the fertilizer products were no longer bagged or packaged, the operation was necessarily local. The fertilizer could be transported no further than the company or the farmer was willing to transport it in bulk (usually between 25-50 miles).

Under this system the bulk-blender kept both the profits from the mixing operation and those of the fertilizer dealer, since the farmer purchased directly from the blender. The farmers’ costs were also reduced significantly; he could now have the fertilizer applied to his field for the price he would have paid for the bagged fertilizer before.

At some time between 1962 and 1972 the Hagerstown plant made the shift to bulk blending. The Company was clearly using granulated materials by 1972 and was providing to local farmers the soil testing and consulting services typical of bulk blenders. Representatives of the company would travel out to different farms in the region, do soil tests, and then recommend particular blends of fertilizers. The plant operation probably worked in the following way during this period (Figure 15):

Granulated fertilizer materials would arrive by train in bottom-unloading hopper cars, which could discharge their contents directly onto a horizontal conveyor system leading up to an elevator. From the elevator different types of fertilizers were channeled into large bins by means of a horizontal conveyor running above the bins (Figures 16, 17, 18). At Central Chemical these bins had concrete floors and wood walls. Eventually a front-end loader would transfer these materials from their storage bins into elevator buckets rising up to be discharged into hopper and then into batch or rotary mixers that operate like those on cement trucks. Finally the mixed product would be carried up another elevator that would discharge into fertilizer-spreader trucks or storage. The Hagerstown plant owned a fleet of trucks designed to apply fertilizers directly to the fields. Farmers could also rent a “buggy” application vehicle that he could pull with a tractor.

Some industry analysts viewed the move to bulk blending as an elimination of dry-mixed bagged operation with retailers simply taking on the additional responsibility of blending the products for the farmers. In this sense, Central Chemical’s switch to bulk blending can be understood as sort of demotion from manufacturer status to that of retailer. Over the course of its whole history we might understand the switch as the final step in the dumbing down of the company. Though in its early years, Central Chemical advertised itself as “Exporters – Manufacturers – Importers,” by the 1970s it had become little more than a middle-man between larger suppliers and farmers. It did not import its own materials, but purchased granulated materials from suppliers. There is no evidence that Central Chemical was exporting products out of the country anymore. And its manufacturing capacity consisted of mixing pre-processed granulated materials in various proportions. At this point, its consulting capacity became equally important to its factory processes.

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